Chapter 5: Adrenal Disorders

Disorders of adrenal function occur at all ages and may be an isolated problem or one of multiple organs involved in certain syndromes. Principles that are helpful in evaluating the most common pediatric clinical situations in which an adrenal disorder is suspected include the following:

1. Patients with early pubic hair development (premature pubarche) will have in order of frequency:

   1. Premature adrenarche

   2. Precocious puberty

   3. Late-onset congenital adrenal hyperplasia (CAH)

   4. Adrenal or gonadal tumor

2. Patients with “simple” obesity are distinguished from those with Cushing syndrome by the following clinical features:

   1. Cushing syndrome often develops rapidly.

   2. Cushing syndrome patients do not grow well in height, but patients with obesity generally have accelerated height growth.

   3. Cushing syndrome patients often have signs of androgen excess.

3. Patients with adrenocortical insufficiency will have either:

   1. Primary adrenal failure, usually with symptoms of both glucocorticoid and mineralocorticoid (ie, salt loss) deficiency. Most commonly seen:

      1. CAH (ambiguous genitalia in females)

      2. Autoimmune Addison disease (often associated with other endocrinopathies)

      3. Adrenoleukodystrophy (ALD)

   2. Lack of adrenocorticotropic hormone (ACTH) stimulation of cortisol secretion, with symptoms of glucocorticoid deficiency alone. Most commonly seen:

      1. ACTH deficiency associated with multiple pituitary hormone deficiencies

      2. Suppression of the hypothalamic-pituitary-adrenal (HPA) axis due to recent discontinuation of corticosteroid treatment

The adrenal cortex secretes three classes of biologically active steroid hormones: glucocorticoids (cortisol), controlled by the HPA axis; mineralocorticoids (aldosterone), controlled through the renin-angiotensin system; and androgens (dehydroepiandrosterone [DHEA] and androstenedione), controlled by an as yet uncharacterized trophic hormone.

Metabolic effects of steroid hormones are mediated by interaction with a specific cellular receptor. The ligand-activated steroid-receptor complex dimerizes, enters the nucleus of target cells, binds to various transcription factors, and forms stable complexes with specific “steroid response elements” that then modulate transcription of specific target genes to exert the hormone effects (see Chapter 1).

The embryologically and functionally distinct adrenal medulla secretes catecholamines, mainly epinephrine (adrenaline), stimulated by the sympathetic nervous system and by high cortisol levels from the adrenal cortex. The effects of epinephrine are mediated through adrenergic receptors, which produce tissue-specific effects.

Anatomy

The adrenal glands lie at the upper pole of each kidney. Ectopic nodules (rests) of adrenocortical tissue derived from embryonic mesenchymal cells may be located in the broad ligaments of the female or in the testes or spermatic cords of the male. The size of the adrenal glands varies with age, mainly due to changes within the adrenal cortex (Figure 5-1). During gestation and at birth, the adrenal glands are much larger relative to body size than during adulthood, and at birth the weight of the glands is nearly that of adult glands (8-12 g). During the first year of life, the adrenal cortex undergoes involution of its fetal component reducing its size by more than 50%. The adrenal glands then gradually increase in size throughout childhood and adolescence. The structure of adrenal circulation facilitates exposure of the medulla to high glucocorticoid concentrations, which stimulate adrenal medullary epinephrine secretion (see section Disorders of the Adrenal Medulla).

Histology

The adult adrenal cortex is divided into three histologically distinct zones: the outer zona glomerulosa, the middle zona fasciculata, and the inner zona reticularis. The zona glomerulosa is site of mineralocorticoid synthesis. There is a gradual transition from glomerulosa to the zona fasciculata, which comprises up to 75% of the cortex and functions in cholesterol storage. There is a clear transition from fasciculata to zona reticularis cells with relatively lipid-free cytoplasm. The cells of the zona reticularis and the clear cells at the interfacebetween the zona fasciculata and zona reticularis are the site of synthesis of glucocorticoids and androgens. The three zones of the adult cortex are mature by 18 to 20 years of age, and show regression associated with aging by 41 to 50 years.

The adrenal medulla is a component of the sympathoadrenal-neuroendocrine system with chromaffin cells (pheochromocytes) arranged in nests and cords, surrounded by a rich vascular network, and their abundant cytoplasm contains catecholamine storage granules. Sympathetic ganglion cells are also present. Epinephrine is the major synthesized and stored catecholamine of the adrenal medulla.

Embryology

The adrenal cortex is derived from mesodermal tissue, the medulla from neuroectoderm. During the fifth week of gestation, mesothelial cells migrate into the underlying mesenchyme (near the developing gonad) and form the fetal zone of the adrenal cortex. A second migration of mesothelial cells arrive to form the smaller definitive (adult) zone. The adrenal cortex is actively synthesizing and secreting steroid hormones during the first trimester in response to tropic hormone stimulation. This is evidenced by androgen overproduction and subsequent ambiguity of the external genitalia in female infants with steroid 21-hydroxylase (CYP21A2) deficiency. During the seventh week of gestation, primitive sympathetic nerve cells differentiate into pheochromoblasts and migrate into the adrenal gland. By the 20th week, these cells have formed clusters of chromaffin cells within the adrenal medulla that does not become a distinct organ until the fetal cortex undergoes atrophy. However, it is functioning at birth as evidenced by the presence of both epinephrine and norepinephrine in the plasma and urine of newborns.

Mechanisms that lead to the differentiation of the adrenal cortex include major effects of transcription factors known as steroidogenic factor 1 (SF-1) and dosage-sensitive sex reversal adrenal hypoplasia congenital (AHC) on the X chromosome gene 1 (DAX-1). SF-1, a member of the nuclear hormone receptor family of zinc finger transcription factors, influences tissue-specific expression of steroidogenic enzymes, the ACTH receptor, the steroidogenic acute regulatory protein (StAR), and müllerian inhibiting substance (MIS). During embryogenesis, SF-1 transcripts are present in the gonads, adrenals, anterior pituitary, and hypothalamus. SF-1 regulates the expression of hormones that are critical for both adrenal functional development and male sexual differentiation, as well as other levels of the endocrine axis such as pituitary and hypothalamic function. SF-1 defects are known to cause congenital adrenal insufficiency as well as disorders of sex development (DSD).

DAX-1, an atypical member of the nuclear receptor family, is the gene responsible for X-linked AHC, in which there is impaired development of the definitive (adult) zone of the adrenal cortex and hypogonadotropic hypogonadism. Both SF-1 and DAX-1 genes are expressed in many of the same sites during embryogenesis, including the gonads, adrenal cortex, pituitary gonadotropes, and the ventromedial hypothalamus, and that DAX-1 is stimulated by SF-1.¹

Nomenclature

The precursor for all adrenal and gonadal steroid hormones is cholesterol. All steroids, therefore, have the same basic structural backbone, the cyclopentanophenanthrene molecule (Figure 5-2). The C₁₈ derivative of this molecule is estrane, C₁₉ is androstane, and C₂₁ is pregnane. Adrenal steroids are derived from the 21- and 19-carbon rings. In general, the C₁₉ steroids are androgens, and when there is a ketone group added at carbon 17 during metabolism, they are excreted in the urine as 17-ketosteroids. The C₂₁ steroids are the mineralocorticoids and glucocorticoids. When a hydroxyl group is added at carbon 17, they are excreted in the urine as 17-hydroxycorticosteroids.

Biosynthesis of Adrenocortical Steroids

The stepwise conversion of cholesterol to adrenal steroid hormones involves a series of enzymes (Figure 5-3), all but one of which belong to the cytochrome P450 family of mitochondrial and microsomal proteins. The adrenal P450s require nicotinamide adenosine dinucleotide phosphate (NADPH) as an electron donor but have differing cofactor requirements. The regulation of adrenal P450 enzymatic activities depends on tropic hormone stimulation, activity of SF-1, physiological demands (eg, intravascular volume, serum sodium concentration, blood glucose), and the gradients of oxygen and steroids across the capillary bed as it passes through the three cortical zones.²

• Conversion of cholesterol to pregnenolone— It is the first and rate-limiting step in adrenal steroidogenesis, mediated by the gene product of CYP11A1 (P450scc, side-chain cleavage), a single enzyme that mediates the three chemical reactions that convert cholesterol to pregnenolone: 20α-hydroxylation, 22-hydroxylation, and cleavage of the cholesterol side-chain bond at position 20-22 (see Figure 5-3). CYP11A1 is under the tropic stimulation of ACTH from the anterior pituitary gland, and requires an intermediate protein, StAR to facilitate access of cholesterol to the enzyme. StAR is expressed in the adrenal cortex and gonads, but not in the placenta (see in the section ACTH Physiology Control of Adrenal Steroid Secretion).

• 3a-Hydroxysteroid dehydrogenase—3β-HSD mediates the conversion of pregnenolone to progesterone and of 17-hydroxypregnenolone to 17-hydroxyprogesterone (see Figure 5-3). This enzyme system requires NAD and is located within the microsomes (endoplasmic reticulum). It is the only steroidogenic enzyme that is not a cytochrome P450, and it is required for the synthesis of glucocorticoids, mineralocorticoids, and sex steroids. There are two highly homologous human 3β-HSD isoenzymes: type 1 and type 2. Type 2 3β-HSD enzyme localizes to the adrenal cortex and gonad and is altered in 3β-HSD-deficiency CAH.

• 17α-Hydroxylase and 17,20-lyase reactions—They convert pregnenolone to 17-hydroxypregnenolone and progesterone to 17-hydroxyprogesterone (17OHP), both of which require hydroxylation at the 17α-position. The subsequent conversion of these two 17-hydroxylated compounds to DHEA and androstenedione, respectively, require 17,20-lyase activity (see Figure 5-3). Both 17α-hydroxylase and 17,20-lyase are enzymatic activities of the same protein, encoded by the gene CYP17A1 or P450c17. CYP17A1 is required for glucocorticoid and sex steroid synthesis, but not for mineralocorticoid synthesis. CYP17A1 is a microsomal cytochrome P450 found in both the human adrenal cortex and testis. The contribution of ACTH to physiologic CYP17A1 transcription remains unclear. CYP17A1 requires an electron transporting cofactor, P450 Oxidoreductase or POR, for normal activity.

• 21-Hydroxylase—It is mediated by the steroid CYP21A2 enzyme (P450c21) (see Figure 5-3), and it converts 17-hydroxyprogesteroneto 11-deoxycortisol and progesterone to 11-deoxycorticosterone (DOC). CYP21A2 is required for the synthesis of both glucocorticoids and mineralocorticoids, but not for the synthesis of androgens. CYP21A2 activity was the first biological function attributed to a cytochrome P450. CYP21A2 is a microsomal cytochrome present in all three zones of the normal adrenal cortex. ACTH stimulation increases concentrations of CYP21A2 messenger RNA (mRNA), but additional factors control CYP21A2 transcription within the functionally different zonae glomerulosa and reticularis, including SF-1. CYP21A2 also requires the electron transporting cofactor, P450 Oxidoreductase or POR, for normal activity.

• 11a-Hydroxylase, 18-hydroxylase, and 18-oxidase—Within the zona glomerulosa DOC undergoes hydroxylation at the 11β-position by CYP11B1 (P450c11) to form corticosterone, which is then converted by 18-hydroxylase (corticosterone methyl oxidase type I [CMO I]) to form 18-hydroxycorticosterone. This product is subsequently converted by 18-oxidase (CMO II) to form aldosterone, the major circulating mineralocorticoid. CMO I and CMO II activities reside within the enzyme CYP11B2 or aldosterone synthase. Within the zona fasciculata, 11-deoxycortisol is converted by CYP11B1 to form cortisol (see Figure 5-3). CYP11B1 and CYP11B2 are mitochondrial cytochromes. As with the above P450s (scc, c17, and c21), CYP11B1 activity and transcription are stimulated in vitro by ACTH and by SF-1.

ACTH Physiology and Control of Adrenal Steroid Secretion

In contrast to cells that secrete peptide or catecholamine hormones, steroid-producing cells do not maintain reservoirs of stored hormone. In addition, steroid hormones, once formed, are highly lipophilic and thus freely permeable to the cell membrane, and specific secretory processes have not been identified. As a result, de novo production of steroids from cholesterol is vital in controlling steroid hormone concentrations. The regulation of steroidogenesis can be viewed at either the level of the organism, with input of complex feedback loops involving the hypothalamus, pituitary, and kidney, or at the level of the adrenocortical cells, where production of steroids is controlled by the specific biochemical events.

Steroid production in the intact organism

Secretion of glucocorticoid by the adrenal cortex is under the control of pituitary ACTH, a single peptide chain of only 39 amino acids. Its half-life in blood is only 7 to 12 minutes. The 1,24 N-terminal amino acid sequence of ACTH has the same steroidogenic activity as the native peptide, and is the peptide sequence of synthetic ACTH used for diagnostic testing. ACTH is one of the differentially spliced products of the proopiomelanocortin (POMC) gene, as described elsewhere.

The hypothalamic factor corticotropin-releasing hormone (CRH) increases ACTH secretion. CRH is a 41 amino acid peptide, stimulated by multiple factors including a diurnal clock, low cortisol levels, and various stresses. CRH activity is located in discrete parts of the hypothalamus, particularly the median eminence. CRH is now known to be an important modulator of body size, not only through its control of ACTH and cortisol secretion but also through its direct anorexigenic effects. Several other peptides homologous to CRH, called urocortins, act in the same manner to regulate food intake.³ Although CRH is the major factor controlling ACTH secretion, other secretagogues are known, such as arginine vasopressin, insulin-induced hypoglycemia, and pyrogen-induced fever. Vasopressin and CRH have a synergistic effect on ACTH release. CRH secretion is inhibited by norepinephrine and stimulated by serotonin.

Control at the cellular level

Temporally, ACTH stimulates steroidogenesisbiphasically. The acute response (seconds to minutes) reflects increased translocation of cholesterol to the inner mitochondrial membrane, where the gene product of CYP11A1 carries out the initial steps in steroidogenesis. This translocation system is induced by cyclic adenosine monophosphate (cAMP), the second messenger for most actions of ACTH, and requires ongoing protein synthesis, suggesting that a labile protein mediates the stimulation. The chronic phase (hours to days) response of steroidogenic cells to trophic hormones largely reflects increased transcription of the steroid hydroxylases in two major areas of gene regulation: cell-selective and hormonally induced expression. Cell-specificity refers to distinct but overlapping patterns of P450 enzyme expression. CYP11A1 is expressed in all classic steroidogenic tissues (adrenal cortex, testicular Leydig cells, ovarian theca cells, and placenta). The CYP17A1 gene likewise is expressed in multiple steroidogenic tissues. In contrast, CYP21A2, CYP11B1, and CYP11B2 are expressed only in the adrenal cortex, with the latter two genes displaying zone-specific expression. Second, the induction of steroid hydroxylase gene transcription is an essential component of the chronic response to trophic hormones, and several different promoter elements and transcriptional regulators have been proposed to confer responsiveness to ACTH.

Glucocorticoid Physiologyand Action

Glucocorticoid secretion is controlled by the HPA axis, as illustrated in Figure 5-4. The control of ACTH secretion is in part determined by the concentration of blood cortisol, the major circulating glucocorticoid. Cortisol in the circulation is 95% protein bound; 90% is bound to corticosteroid-binding globulin (CBG) or transcortin. Transcortin has a high affinity for cortisol as well as progesterone and can bind prednisolone and aldosterone, but not dexamethasone. The free fraction of cortisol is biologically active and is about 8% of the total cortisol when serum concentrations are normal. Compounds that bind to transcortin (eg, prednisone) will displace cortisol. At normal serum concentrations, the half-life of endogenous cortisol is 60 to 80 minutes; this may increase up to 2 hours at higher concentrations. Cortisol, both free and bound, is distributed rapidly and widely throughout the body compartments, including the extracellular fluid.

The sulfation and glucuronidation metabolism of all steroid hormones occurs mainly in the liver, from which they return to the circulation through the hepatic vein to be excreted mainly by the kidney (∼90%), or excreted into the intestinal lumen through the bile. The kidney also acts as a site of the inactivation of cortisol to cortisone. Tetrahydro metabolites have been historically measured as urinary 17-hydroxycorticosteroids (17-OHCS), although the routine use of the test has been replaced by measurement of serum concentrations of specific steroids.

Glucocorticoid actions are mediated by interaction of naturally occurring and synthetic (pharmacological) steroid hormones with the glucocorticoid receptor (GR) or type 1 steroid hormone receptor. Genetic variation within the GR gene may confer increased or decreased glucocorticoid sensitivity.⁴

Glucocorticoid effects on carbohydrate metabolism are widespread (Table 5-1) and, at physiologicconcentrations, counterbalanced by effects of other hormones. The term “glucocorticoid” denotes effects on production and storage of glucose, so-called anti-insulin or glucose-sparing actions. Cellular glucose uptake and utilization are inhibited and glycogen synthesis stimulated. Amino acid and free fatty acid substrates for gluconeogenesis are mobilized from plasma and muscle proteins, leading to increased urinary nitrogen excretion and induction of urea cycle enzymes. In states of glucocorticoid excess, these effects may produce insulin resistance and hyperglycemia.

Glucocorticoids exert a lipolytic action, which produces substrates for gluconeogenesis and glycogen synthesis. In hypercortisolemia, however, lipogenesis and obesity are mediated by the combined actions of excess cortisol and insulin, which stimulate appetite and produce the characteristic change in body fat distribution (central obesity, “buffalo hump”).

In addition to metabolic effects, other glucocorticoid effects include anti-inflammatory and immunosuppressive actions via direct effect on cells of the immune system, inhibition of wound healing, skeletal growth retardation and loss of bone mineral, decreased vitamin D–mediated calcium absorption from the gut, psychiatric disturbances such as depression and psychosis, and fluid and electrolyte disturbances that may be mediated through the mineralocorticoid or type 2 steroid hormone receptor.

Mineralocorticoid Physiologyand Action

Control of aldosterone secretion by therenin-angiotensin system

Renin is a proteolytic enzyme that converts angiotensinogen in the liver to angiotensin I, which has mild vasopressor properties. Renin secretion from the renal juxtaglomerular cells is controlled by a baroreceptor system of the arterioles located in their proximity. Proteolytic cleavage of angiotensin I by angiotensin-converting enzyme (ACE) in the lungs produces the octapeptide angiotensin II that is a potent vasoconstrictor (Figure 5-5) and stimulates production of the major adrenal salt-retaining steroid, aldosterone. An increase in aldosterone augments increased sodium and water retention with increased intravascular volume. The resultant stretching of the renal arterioles results in decreased secretion of renin. Inversely, a decrease in blood volume as can occur in dehydration, hemorrhage, or low-salt diet will increase renin secretion.

Although angiotensin II is the major stimulator of aldosterone secretion, ACTH has a definite but temporary effect as well. By contrast, prolonged and constant ACTH stimulation results in a sustained increase in plasma cortisol concentrations, but a progressive fall of aldosterone concentrations as the renin-angiotensin system is suppressed by aldosterone release and mineralocorticoid effect of the high cortisol levels.

Potassium also directly increases secretion of aldosterone by the zona glomerulosa. Although the most potent mineralocorticoid is aldosterone, some mineralocorticoid activity is found in DOC. Circulating aldosterone is bound to transcortin with 10% of the affinityof cortisol and has a plasma half-life of approximately 45 minutes. Virtually aldosterone that enters the hepatic circulation is converted to two primary metabolites, tetrahydroaldosterone and aldosterone-18-glucuronide, which are excreted in the urine.

Mineralocorticoid actions are mediated by the interaction of steroid hormones with the mineralocorticoid receptor (MR) or type 2 steroid receptor. In humans, the major natural mineralocorticoids are aldosterone and DOC. However, the MR binds also glucocorticoids such as cortisol and corticosterone with affinities similarto aldosterone. Within the major mineralocorticoid target site, the kidney, tissue-specific 11β-HSD type 2 promotes the efficient conversion of cortisol to inactive cortisone, thus removing cortisol as a significant ligand of the MR in that tissue.

Mineralocorticoids control the excretion of electrolytes, mainly in the kidney. Through ligand-receptor complex stimulation of specific ion transport channels, aldosterone enhances cortical collecting duct reabsorption of sodium, increases chloride and water retention, and thereby expands extracellular volume. Defects in these subtypes of chloride channels can cause aldosterone resistance (pseudohypoaldosteronism). Within the outer portion of the medullary collecting duct, aldosterone enhances proton excretion, particularly potassium ions. Stimulation of potassium excretion is dependent on sufficient sodium intake. Sodium conserving and potassium wasting effects of aldosterone are also present in salivary and sweat glands, and in the gut.

Effects of mineralocorticoid excess (eg, in primary hyperaldosteronism) include hypokalemia, metabolic alkalosis, and hypertension. Whereas hypokalemia and hypervolemia seem natural consequences of mineralocorticoid excess, the basis for metabolic alkalosis is unclear. It is postulated that severe potassium deficiency may alter normal acid excretion by the renal tubule.

Adrenal Androgen Physiology and Action

The secretion rate of cortisol and adrenal androgens are divergent. Prepubertal children secrete cortisol at a rate (corrected for body size) similar to that of adult subjects, but adrenal androgens are almost undetectable during childhood and increase markedly at puberty without any change in ACTH or cortisol secretion. Cortisol secretion also remains similar with adult aging, while the concentrations of adrenal androgens in blood fall. In premature adrenarche, when adrenal androgens prematurely reach adult concentrations resulting in appearance of pubic hair, the cortisol secretion remains normal for size. The identity of a peptide-regulating adrenal androgen secretion remains elusive.

The adrenal androgens are DHEA, its sulfated form DHEA-sulfate (DHEA-S), and androstenedione. Both compounds exert their biological effects through extra-adrenal conversion to the potent androgens testosterone and dihydrotestosterone (DHT), which then interact with the androgen receptor (AR) within androgen target tissues (Figure 5-6A). Human steroidogenic enzymes also catalyze steps in an alternative pathway of DHT production (Figure 5-6B) referred to as a “backdoor pathway.”⁵ This pathway has clinical relevance in 17-hydroxylase deficiency CAH.⁶

Circulating androstenedione and DHEA bind to sex-hormone–binding globulin (SHBG) to a much greater degree than to transcortin, but to a lesser degree than testosterone and DHT binding to SHBG. The plasma half-life of DHEA is relatively brief at approximately25 minutes. DHEA-S, produced in both liver and adrenal cortex, has a relatively long half-life of 8 to 11 hours and undergoes very little hepatic extraction or renal clearance. Adrenal androgens are metabolized to some degree in the liver; however, a significant degree of production and interconversion of the sex steroids occur in gonads, skin, and adipose tissue.

In adults, 15% of the circulating androstenedione is produced by peripheral conversion of DHEA and testosterone. The remainder is produced by relatively equal contributions from the adrenal and the gonad. Androstenedione is reversibly converted to testosterone by the enzyme HSD17B3 (17-ketosteroid reductase). Androstenedione may also be converted to estrone by aromatase (Figure 5-6A). Measurement of urinary 17-ketosteroids (17-KS), once commonly used as an assessment of adrenal androgen production, measures conjugated and unconjugated C₁₉, 17-keto compounds; DHEA and androstenedione are the major precursors of the urinary 17-KS, whereas testosterone and its metabolites contribute very little.

The physiologic roles of DHEA and androstenedione in their native state remain controversial. DHEA treatment does not significantly alter perimenopausal symptoms or body composition in the elderly, but in women with adrenal insufficiency, improvement in sexualinterest and sense of well-being are reported. Effects on insulin sensitivity, body fat stores, lipid profiles, energy metabolism, and insulin-like growth factor levels remain unresolved.

Fetal Life

The fetal adrenal is deficient in 3β-HSD, and yet cortisol production is evident by 10 weeks of gestation. This is made possible by passage of 3β-hydroxysteroids (and their sulfates) from the fetus to the placenta, which has abundant 3β-HSD and sulfatase (Figure 5-7). Progesterone and 17-hydroxyprogesterone produced in the placenta return to the fetus and are converted to cortisol and aldosterone, respectively.

Cortisol preparations administered to the mother only minimally cross the placenta early in gestation because only unbound cortisol can be transferred to the fetus. In addition, both placenta and fetus have 11β-HSD type 2 (11β-HSD2) activity that forms inactive cortisone from cortisol. The mother contributes approximately 20% of the total fetal cortisol and 75% of fetal cortisone, the balance being secreted by the placental-fetal unit. As a consequence, to accomplish glucocorticoid therapy for the fetus (eg, CAH), it is necessary to administer a steroid-like dexamethasone that does not bind to transcortin and is not readily metabolized.

From mid-pregnancy to term, fetal plasma cortisol levels (∼2 μg/dL) are much lower than in the mother. In contrast, newborn concentrations of aldosterone are about twice those of the mother.

The relative deficiency of 3β-HSD activity in normal fetal adrenals results in the formation of large amounts of DHEA-S and its 16-hydroxy derivative. The 16-OH-DHEA is transferred into the placenta where sulfatase and aromatase transform 16-OH-DHEA into estriol. Whereas estrone and estradiol arise mainly from placental synthesis, estriol has its main origin in the fetal adrenal (see Figure 5-7). This explains why a drop in urinary estriol in pregnancy suggests either abnormal placental function, or poor fetal adrenal function.

Neonatal Period and Infancy

There is little or no diurnal variation of glucocorticoid concentrations in early infancy, both in preterm and full-term infants. Studies of healthy infants show that a diurnal pattern of cortisol secretion is unlikely before 1 month of age and that most infants show a normal diurnal pattern by about 6 months of age. The appearance of the diurnal pattern seems to correlate with the development of a normal night/day sleep/wake cycle.^7,8

As the fetal adrenal cortex lacks sufficient activity of some of the enzymes required for efficient cortisol secretion, it is not surprising that plasma cortisol concentrations in preterm infants, especially in response to stress and illness, are in the range considered “deficient” in full-term and older infants. The adrenal cortex of preterm infants continues to produce the major products of the fetal cortex, and without the placenta it lacks the substrates needed for sufficient cortisol secretion. Urinary excretion of “fetal zone” steroid metabolites that persists until the postconceptual age approaches 40 weeks suggests that involution of the fetal zone, and development of the definitive zone is not accelerated by premature birth. In preterm infants, there is a gestational age-related decrease in inactive cortisone concentrations relative to cortisol and a lower cortisol and 17-hydroxyprogesterone response to ACTH at less than 30 weeks’ gestation, when compared to 30 to 33 weeks. In sick preterm infants on ventilators, the cortisol response to ACTH stimulation is lower than in gestational age matched healthier infants.⁹

Cortisol production rates: infancy and beyond

Knowledge of the cortisol production rates in normal subjects forms the basis for cortisol replacement dosage recommendations in patients with adrenal insufficiency. In normal subjects of various ages, cortisol production increases with body size. In the analysis of subjects of all ages, when the values are corrected for body surface area, the average ± SD is 12.1 ± 1.5/m²/24 h (Figure 5-8A). In the first week of life the values are somewhat greater than those of the children and adults, coming down to that range after 3 to 4 weeks of age. In children older than infants and toddlers, the cortisol production rate is estimated at 6.8 ± 1.9 mg/m²/24 h (Figure 5-8A).

During the first 10 days of life in full-term infants, the cortisol secretion rate corrected for body size is about 1.5 to 2 times higher than it is later in infancy, childhood, and adulthood (see Figure 5-8A). In contrast, the aldosterone secretion is the same from infancy to childhood and adulthood. The concentrations of aldosterone in infancy tend to be higher than those observed later on in childhood.

Plasma adrenal androgens (DHEA, DHEA-S, androstenedione) and urinary 17-ketosteroids are relatively high shortly after birth but fall to low concentrations after 4 to 6 weeks of age, reflecting involution of the fetal zone of the adrenal cortex. In addition, plasma levels of 17-hydroxyprogesterone are high during the first 24 hours of life. It is important, therefore, to obtain a newborn screen sample after 24 hours of age to minimize the risk of a false-positive screen for CAH.

Childhood

During childhood, puberty, and adulthood, cortisol secretion rate corrected for body surface area remains constant and blood cortisol concentrations follow their expected diurnal variation (Figure 5-9; see Figure 5-8). Aldosterone secretion rate and plasma concentrations are similar in childhood, puberty, and adulthood. In childhood, adrenal androgen secretion is quite low.

Normal and Premature Adrenarche

In the few years prior to gonadal maturation and puberty, under the stimulation of an as yet uncharacterized substance, there is increased secretion of DHEA, DHEA-S, and androstenedione with no change in ACTH concentration in blood or cortisol secretion rate corrected for body size (Figure 5-10) and this state is called adrenarche. As seen with the timing of gonadal puberty, adrenarche occurs 1 to 2 years earlier in girls than in boys. In both sexes the rise in plasma levels of adrenal androgens occurs before physical evidence of androgen effects are noted. In children with hypopituitarism, a lack of adrenarche is often noted. This leads to the supposition that there is a pituitary or hypothalamic factor that stimulates adrenarche. Premature adrenarche is the state in which adrenal androgen maturation occurs much earlier than gonadal maturation, producing signs of androgen effect before the expected age.

Premature adrenarche, more common in girls, is characterized clinically by appearance of pubic and/or axillary hair owing to premature adrenal androgen secretion before age 8 years in the absence of breast development. There remains controversy in the actual age that defines “premature” development. Premature sexual hair growth, body odor, and mildly increased height velocity, and/or skeletal age are typical. In the majority of children with premature adrenarche, the etiology is unknown. While most children go on to experience normal puberty, some appear to be at increased risk for early development of metabolic syndrome and (in girls) polycystic ovary syndrome (PCOS) (ovarian hyperandrogenism).¹⁰ It is unknown at this time whether the premature adrenarche itself or its association with high body mass index (BMI) or certain ethnic groups confers the increased risk of insulin resistance and ovarian hyperandrogenism.

Box 5-1 lists the circumstances in which a patient with premature adrenarche should be referred to a pediatric endocrinologist.

Pregnancy

• Cortisol—During pregnancy, estrogen-stimulated increases in transcortin concentration cause greater binding capacity for cortisol, a rise in plasma concentrations of total cortisol, and an increase in its half-life. Unbound cortisol concentrations are also elevated. At the same time, cortisol secretion is decreased during pregnancy, so that replacement therapy in pregnant women with hypoadrenocorticism typically consists of usual dosages. At the time of labor, cortisol therapy should be increased to stress levels in pregnant women with hypoadrenocorticism.

• Aldosterone—Pregnant women have increased plasma renin activity (PRA), plasma aldosterone concentrations, and aldosterone secretion rate, likely reflecting a stimulation of the renin-angiotensin-aldosterone system due to a progesterone-mediated salt-losing tendency. Unlike cortisol, aldosterone does not have a specific binding protein; its binding does not increase significantly during pregnancy and its half-life in blood does not change markedly.

• Androgens—Maternal DHEA-S concentrations are decreased in pregnancy. The cause for this long-described phenomenon is unknown but is postulated to be associated with increased 16-hydroxylase activity leading to the production of estriol.

Stressful conditions are often associated with increased adrenocortical secretion of cortisol, secondary to increases in CRH and ACTH output. The increase in cortisol levels with stress is a mediator of the adrenal medullary catecholamine response to stress. Stress conditions can be classified into surgical (trauma, anesthesia, tissue destruction), medical (acute illness, infection, fever, hypoglycemia), and emotional (psychological). It is not clear whether the mechanism stimulating adrenal function is unique or different for each type of stress.

Regarding infection, hormones of the HPA axis interact with components of the immune system in a complex manner. The cytokine interleukin-1 (IL-1) is secreted by macrophages in response to microbial invasion, inflammation, immunologic reaction, and tissue injury. IL-1 then activates and increases T cells, accelerates the transformation of B cells into plasma cells, which then produce antibodies. In addition, IL-1 activates the CRH-ACTH-cortisol system; the increased cortisol concentration in plasma results in a negative feedback on the macrophages. Other cytokines including tumor necrosis factor-α (TNF-α) and IL-6, as well as IL-1, stimulate CRH release but are inhibited by cortisol. The endocrine immune system interactions are influenced reciprocally by the autonomic nervous system.¹¹

Products of the POMC gene, collectively calledmelanocortins (ACTH, α-, β-, and γ-melanocyte stimulating hormone [MSH]) interact with specific receptors on leukocytes. These receptors mediate both immunomodulatory and anti-inflammatory effects independent of production of cortisol. In addition, there are central neurogenic anti-inflammatory melanocortin-stimulated signals that utilize both adrenergic and cholinergic pathways.

Obesity

Obesity related to high caloric intake is usually accompanied by an increase in cortisol secretion rate, concomitant decrease in cortisol half-life, and normal plasma concentrations. Urinary free cortisol excretion can be elevated, but when corrected for body surface area or creatinine excretion, values usually normalize. In the minority (∼20%) of obese subjects with values that remain elevated after correction for body size, other tests to rule out Cushing syndrome may be necessary.

Investigation of cortisol/cortisone metabolism in obesity has resulted in new insights. The enzyme 11β-HSD type 2 converts cortisol to inactive cortisone mostly in the kidney, whereas 11β-HSD type 1 catalyzes reactivation of cortisone to cortisol mostly in liver and adipose tissue. These two enzymes are functionally similar but are encoded by different genes on different chromosomes.

Malnutrition/Anorexia Nervosa

Low-calorie or protein intake is associated with elevated plasma cortisol levels. This results partly from increased secretion, and also from increased half-life due to low metabolic rate. Cortisol response to ACTH stimulation is normal, but response to CRH is blunted. Absence of cushingoid features suggests a degree of cortisol resistance. Following rehabilitation, plasma cortisol concentrations normalize.

Thyroid Disorders

Hypothyroidism results in slower metabolism and hyperthyroidism results in faster metabolism of cortisol, but patients with thyroid disorders tend to maintain normal plasma cortisol concentrations by either decreasing cortisol secretion in hypothyroidism or increasing it in hyperthyroidism. It should be noted that cortisol deficiency may be masked by hypothyroidism, and restoring such patients to the euthyroid state may precipitate symptoms of adrenal insufficiency. Therefore in a patient with hypopituitarism, cortisol replacement should be initiated prior to thyroxine replacement.

Growth Hormone Deficiency

In patients diagnosed with growth hormone deficiency, it is important to test the HPA axis, as the risk of ACTH deficiency is present in any patient with one established pituitary hormone deficiency. Short children with growth hormone deficiency (and normal ACTH reserve) are compared with short children who do not have growth hormone deficiency; the diurnal patter of cortisol secretion are not different.

Hepatic Disease

The liver extracts a large fraction of plasma steroids for metabolism, usually by reduction and by conjugation to glucuronic acid. Advanced hepatic failure results in decreased cortisol clearance and a prolonged half-life; thus plasma cortisol remains normal.

Renal Disease

Because large fractions of cortisol and aldosterone metabolites are excreted in urine, renal failure causes lower excretion of steroid metabolites. However, the secretion of cortisol and its plasma concentration usually remains normal. As noted earlier, hyperkalemia in renal failure has a direct effect on increasing aldosterone secretion.

Critical Illness

In patients with normal adrenal responsiveness to the stress of severe infection, plasma cortisol levels will increase 3- to 10-fold, unless the sepsis has caused bilateral adrenal hemorrhage. In both adults and children with septic shock, an inadequate basal cortisol level and/or an inadequate cortisol response to IV ACTH correlates highly with poor outcome. This adrenal insufficiency during stress is believed to be maladaptive and results in unchecked actions of cytokines. The lessons learned from septic shock have been expanded to include other forms of critical illness. Definite guidelines for diagnosis and treatment of cortisol deficiency in these settings have been established (Figure 5-11).¹² The guidelines for the use of hydrocortisone for hemodynamic support in pediatric septic shock suggest cutoffs similar to those shown in Figure 5-11. The doses of hydrocortisone recommended for hemodynamic support in septic shock are far higher than those used for “stress coverage” in healthy patients with a history of adrenal insufficiency.¹³

Dichlorodiphenyltrichloroethane (DDT), its -dichloroethanederivative (DDD), and related compounds such as o,p’-DDD can suppress adrenal cortical function. The latter substance is used in the treatment of adrenal carcinoma with some success but is often poorly tolerated because of nausea, anorexia, and protracted vomiting.

Another substance, 1,1 bis-(p-aminophenyl)-1-methyl-propanone, called amphenone B, can also suppress adrenal function. This compound and o,p’-DDD tend to produce a destruction of the cells of the adrenal cortex rather than to specifically inhibit its function.

Aminoglutethimide appears to block CYP11A1, thereby inhibiting transformation of cholesterol to pregnenolone. Aminoglutethimide also has inhibitory effects on CYP11B1, reducing cortisol and aldosterone production.

The antifungal agent ketoconazole is known to generally suppress cytochrome P450 enzyme activity. This is associated with a blunted cortisol response to ACTH and thus has a risk of inducing adrenal insufficiency. It has been used therapeutically to suppress adrenal androgen excess in patients with CAH, cortisol excess in Cushing syndrome, and gonadal androgen secretion in boys with precocious puberty. Other drugs that inhibit mitochondrial P450s and thus impact steroid synthesis include fluconazole and etomidate, and potentially others that are currently under investigation.

In addition to compounds that directly affect enzymes involved in adrenal steroid biosynthesis, others have their effect at the target cell level. The aldosterone antagonism effects of spironolactone, progesterone, and 17-hydroxyprogesterone relate to their ability to compete for the MR.

Drugs associated with increased cortisol metabolism include phenobarbital, phenytoin, rifampin, and troglitazone. Peripheral resistance to glucocorticoids has been described with mifepristone through interaction with the GR, and psychotropic drugs (chlorpromazine, imipramine) can inhibit glucocorticoid-induced gene transcription. Anticoagulants may cause adrenal insufficiency indirectly by causing adrenal hemorrhage.

The progestational agent megestrol acetate (Megace), a potent appetite stimulator used in patients with cachexia, may suppress adrenal function by binding the GR and activating the negative feedback loop that inhibits ACTH and cortisol secretion. In a few patients on high doses, its interaction with the GR has caused Cushing syndrome.

Disorders of deficient or excess adrenocortical function can be diagnosed with proper selection of tests of basal HPA function and dynamic tests of HPA axis capacity.

Tests of Glucocorticoid Secretion

Plasma cortisol

The plasma concentrations of total and free cortisol, the main human glucocorticoid, are determined accurately using HPLC tandem mass spectrometry assays.

Pulsatile secretion and diurnal variation of cortisol: Because cortisol is secreted in a pulsatile manner, small variations can be observed when blood samples are collected at frequent intervals. The episodic secretion of ACTH and cortisol with time results in the diurnal or circadian variation (rhythm) of plasma ACTH and cortisol concentrations, with a surge of secretion between4 and 6 am, followed by decreasing concentrations to their lowest levels in the evening and during the night. Thus it is important to obtain plasma samples for analysis of basal cortisol or ACTH secretion at appropriate times given the clinical situation: usually 8 am for tests of cortisol sufficiency and/or 4 pm for tests of cortisol excess. Stressful situations are likely to raise the ACTH and cortisol concentrations, including anxiety and pain associated with phlebotomy.

The circadian rhythm is related to sleep-wake cycles. Modification of the sleep-wake distribution throughout a 24-hour period changes the profile of cortisol concentrations, as long as the modification is maintained for a sufficient time. The rhythm of cortisol can be altered by strict sleep reversal, but night workers with a variable schedule tend to maintain a normal diurnal rhythm. Blind subjects may also have disturbances of the normal diurnal pattern.

Urinary free cortisol

Unbound or free plasma cortisol is excreted by the kidney. As only free plasma cortisol is biologically available, the fraction of unbound plasma cortisol that is excreted in urine as free cortisol reflects glucocorticoid activity at the cellular level. Current assays show only 1% to 2% cross-reactivity with some steroids (cortisone, corticosterone, 11-deoxycortisol, and 17-hydroxyprogesterone), but prednisolone has about 30% cross-reactivity. The range of urinary free cortisol for normal adults varies by laboratory, and this range is 10 to 35 μg/24 h in females and 10 to85 μg/24 h in males. When corrected for urinary creatinine concentration, the range is approximately 8 to 40 μg/g of creatinine. In children, the range is approximately 3 to 9 μg/24 h, and when the values are correlated with body size, the range corrected for body surface area being 25 to 65 μg/m²/24 h. When corrected for urinary creatinine, the range is approximately 7 to 25 μg/g creatinine. During pregnancy the reference ranges are higher. In Cushing syndrome the concentrations are usually above 150 μg/24 h and in adrenal insufficiency less than 10 μg/24 h.

Salivary cortisol

Salivary glands and sweat glands excrete only unconjugated, unbound (free) glucocorticoids. Salivary samples can be collected at home in a nonstressful setting. The diurnal pattern of salivary cortisol concentration reflects those of total plasma cortisol, but concentrations are about 90% lower. This is due in part to the metabolism of cortisol to cortisone by the salivary glands, as well as the fact that it measures free, not total, cortisol. Nighttime salivary cortisol concentrations have been validated as a useful screening test for Cushing syndrome in both adults and pediatric patients,¹⁴ and this remains its most significant clinical use. It is replacing the 24-hour urinary free cortisol as the initial screening test. A midnight salivary cortisol level greater than 0.44 mg/dL identifies pediatric patients with Cushing syndrome with 99% specificity and 100% sensitivity.¹⁵

The use of salivary cortisol levels in clinical medicine has expanded, especially in the area of neurobehavioral studies that examine responses to stress. In the setting of endocrinology, salivary cortisol is not a reliable method for diagnosing adrenal insufficiency. It has been studied as a tool to monitor replacement therapy in patients with adrenal insufficiency and CAH; however, the levels are highly variable and have not added significant information in the monitoring of these patients.^16,17

Time-based reference ranges for salivary cortisol concentrations are similar in prepubertal children and adults. The approximate ranges at 0800 are 0.17 to 1.2 mg/dL; at 1600, 0.10 to 0.3 mg/dL; and at 2300, 0.03 to 0.17 mg/dL. After a 1-mg dose of dexamethasone at 2300, the following morning 0800 salivary cortisol should be less than 0.1 mg/dL.

ACTH

Plasma ACTH can be measured accurately by immunometric assays. As with cortisol, it is important to standardize the time at which blood samples are collected, usually at 8 am (normal range 20-120 pg/mL) and 4 pm (0-50 pg/mL). Because cortisol has a negative feedback on ACTH secretion (ie, when cortisol concentrations are elevated, those of ACTH tend to decrease, and reciprocally), it is often helpful to measure simultaneously the cortisol and ACTH concentrations.

CRH

Assay techniques for the measurement of CRH concentration are available, but determining its concentration in plasma is not often useful. Because CRH reaches the anterior pituitary corticotrophs via a portal system of vessels, studies of CRH in peripheral circulation have not been fruitful. It is probable that there is a diurnal variation of CRH in the pituitary portal vessels, but a diurnal pattern has not been observed in plasma.

Tests of HPA axis capacity

ACTH stimulation tests.

After prolonged loss of ACTH secretion, such as in states of cortisol excess or in hypopituitarism, the adrenal cortex can become resistant to its stimulatory effect.¹⁸ The rapid IV ACTH test is often used to screen for ACTH deficiency in such patients. In this setting, either a low-dose (0.1-1 μg) or high-dose (250 μg) test has been used. The 250-μg test is widely used, and the cortisol response 30 to 60 minutes after injection should peak at or above 18 to 20 μg/dL to rule out adrenal insufficiency. The 1-μg test, though, may be more sensitive in detecting milder degrees of adrenal gland suppression. The expected cortisol response to the low-dose test is reported by some authors to be slightly less than with the high-dose test¹⁹ but by others to be the same as the high-dose test.¹⁸ However, the cortisol response to insulin-induced hypoglycemia remains the gold standard, and the peak cortisol levels seen with the 250-μg ACTH test are comparable to those seen with insulin-induced hypoglycemia.¹⁹

In critically ill patients, especially those with sepsis or hemodynamic instability, screening for relative adrenal insufficiency involves measurement of blood cortisol before and 30 to 60 minutes after 250 μg of IV ACTH. In this stressful setting, basal levels of cortisol should normally exceed 30 μg/dL; if less than 15 μg/dL and if the cortisol concentration does not rise by at least 9 μg/dL over baseline values that are less than 30, relative adrenal insufficiency is suspected.

Tests of anterior pituitary ACTH reserve

Glucagon stimulation test.

Because glucagon stimulates both ACTH and growth hormone secretion, the glucagon test can be used to assess both cortisol release and pituitary reserve of ACTH secretion. A baseline sample is drawn, followed by a 0.03-mg/kg (to a maximum of 1 mg) dose of glucagon given by SQ (or IM) injection. Serum cortisol can be measured every 30 minutes, up to 3 hours following the administration of glucagon. Patients, in particular young children, can experience abdominal discomfort, nausea, and/or vomiting during the course of the glucagon stimulation test.²⁰ The cortisol response is similar to that seen with the ACTH stimulation tests.

CRH stimulation test.

Another IV administration of ovine CRH (100 μg/dose) is normally followed by an increase in plasma ACTH from approximately 8 to 25 pg/dL with a concomitant increase in plasma cortisol. The ACTH response to CRH may be useful in the differentiation of Cushing from pseudo-Cushing syndrome. Normative data now exist for ACTH response to CRH test in very-low-birth-weight infants, in whom antenatal maternal corticosteroid treatment may induce adrenal suppression.

Insulin tolerance test.

Hypoglycemia is a potent stimulus for ACTH secretion. At 8 am after an overnight fast, 0.05- to 0.075-U/kg regular insulin is given by IV injection. Serum glucose and cortisol are measured at baseline and every 15 minutes for 1 hour. A normal response is seen if the 8 am baseline cortisol concentration is within the expected reference range, and the level doubles or rises over 20 μg/dL with hypoglycemia. Basal cortisol and the insulin tolerance test (ITT) are thought to be more accurate for detection of HPA axis deficiency than is the CRH test or the low-dose (1 μg) ACTH test; however, it is contraindicated in some patients such as infants.¹⁸

Testing for ability to suppress ACTHand cortisol secretion

Dexamethasone suppression test.

Administration of a potent glucocorticoid, such as dexamethasone, provides negative feedback suppressing ACTH secretion and secondarily decreasing cortisol secretion. There are several types of dexamethasone suppression tests (Table 5-2). One method uses a single nighttime dose of 1 mg followed by measurement of 8 am cortisol. More prolonged “low-dose” and “high-dose” tests last several days and are followed by measurement of plasma ACTH and cortisol. The test is useful in the evaluation of patients with suspected Cushing disease. Dexamethasone suppression test may also differentiate whether hyperandrogenemia in a female results from adrenal or gonadal secretion, the latter not being sensitive to ACTH suppression.

Tests of Mineralocorticoid Secretion

Nonspecific tests, such as electrolytes in serum and in urine, as well as occasionally in sweat and saliva, can aid in diagnosing abnormalities in mineralocorticoid secretion or action. However, precise immunoassays for aldosterone and PRA provide a direct assessment of mineralocorticoid secretion and its control by the renin-angiotensin system.

Plasma aldosterone

Plasma concentrations of aldosterone follow a circadian variation that is similar to but less marked than that of cortisol. Aldosterone concentrations change slowly (24-48 hours) in response to high- or low-sodium intake. In contrast, changes in body position (standing vs lying down) bring about rapid but transient variation in aldosterone concentrations.

In early infancy, plasma aldosterone concentrations are variable but in general are elevated relative to older children and adults. After 1 year of age and up into adulthood, mean values remain constant, although there are large individual variations.

Aldosterone secretion rate

Aldosterone secretion rate is relatively constant throughout life, so that recommended replacement doses of 9α-fluorocortisol in patients with mineralocorticoid deficiency are similar throughout childhood and adulthood. There are slighter lower values observed during the first 2 weeks after birth, but the blood levels of aldosterone are higher. Changes in sodium diet influence the aldosterone secretion rate as well as plasma concentrations of this steroid.

Plasma renin

Plasma renin activity.

PRA is measured by the rate of release of angiotensin II from the renin substrate angiotensinogen. The angiotensin II being formed is measured by immunoassay and the PRA is expressed as angiotensin II formed in pg/mL of plasma per hour. PRA shows episodic variation as well as mild diurnal variation. On an average sodium intake the PRA is 10 to 50 pg/mL/h. Concentrations increase markedly during a low-sodium diet and are suppressed by a high-sodium diet. PRA may be elevated in patients who are receiving certain medications, such as ACE inhibitors, vasodilators, diuretics, and spironolactone.

Direct renin measurement.

Direct determination of renin concentration in plasma is made with a specific immunoassay. Normal ranges vary based on sodium intake, posture, and age.

Tests of Adrenal Androgen Secretion

Clinical signs suggesting hypersecretion of androgens should prompt measurement of their concentration in blood. In the prepubertal male, they include increase in size of the penis; scrotal pigmentation and thinning, pubic, axillary, and facial hair; and deepening of the voice. In the female, they include premature pubarche, enlargement of the clitoris, deepening of the voice, disruption of menstrual cycling, and hirsutism.

Plasma androgens

The main adrenal androgens include androstenedione, DHEA, and DHEA-S (see Figure 5-6A). Their plasma concentrations are typically measured by HPLC tandem mass spectrometry. These steroids do not bind to the androgen receptor and therefore have negligible biological activity. However, 5% to 10% of DHEA is converted to androstenedione, and a similar fraction of androstenedione is converted to testosterone.

Adrenal androgens have very little significance in adult males, but they contribute about 75% of the testosterone in adult women. The life cycle of plasma concentrations of adrenal androgens is shown in Figure 5-10. The concentration of DHEA-S in plasma is the best indicator of adrenarche during pubertal maturation. Among hormonal steroids in human plasma DHEA-S has by far the highest concentrations, owing to its long half-life.

Urinary 17-ketosteroids

Androgens, whether secreted by the adrenals or by the gonads, are partially metabolized into 19-carbon steroids with a 17-ketone and are excreted as urinary 17-ketosteroids. About one-third of testosterone produced in the body is excreted in the urine as 17-ketosteroids. The conversion of androstenedione to testosterone is a reversible reaction catalyzed by HSD17B3; thus a portion of circulating testosterone is converted back to a 17-ketosteroid. Normal values are low before puberty (< 2 mg/24 h), compared with adolescence and adulthood. Normal values in adults are higher in males than females (7-17 mg/24 h vs 4-13 mg/24 h). Although most providers prefer to measure specific plasma androgens, the determination of urinary 17-ketosteroids can still be useful in specific situations, such as when phlebotomy is not feasible or assessment of 24-hour integrated adrenal androgen production is warranted.

Hypoadrenocorticism

Disorders of hypoadrenocorticism can be classified as either intrinsic to the adrenal cortex (primary hypoadrenocorticism), due to CRH/ACTH deficiency (central or secondary hypoadrenocorticism), or due to unresponsiveness to trophic or adrenocortical hormones (Table 5-3).

Signs and symptoms of adrenocortical insufficiency depend on the hormones that are deficient (Table 5-4), and/or in excess (eg, androgens) in patients with biosynthetic defects of cortisol and aldosterone. Clinical features of chronic hypoadrenocorticism may be influenced by other symptoms resulting from the autoimmune polyglandular syndromes (APS) (Table 5-5).

Treatment of adrenal insufficiency consists of hormone replacement therapy. In primary adrenal insufficiency, both glucocorticoid and mineralocorticoid treatment is usually needed. This group of patients is at risk for a salt-wasting crisis at the time of diagnosis or duringtimes of stress. In isolated cortisol deficiency (eg, due to ACTH deficiency or resistance), only glucocorticoid treatment is needed. In all patients, the dose of glucocorticoid must be increased during times of stress. A detailed description of treatment protocols is given as follows.

Primary hypoadrenocorticism

Causes of primary hypoadrenocorticism can be classified based on physiology and embryology (see Table 5-3). Lack of differentiation of adrenal cortex results in congenital adrenal aplasia or hypoplasia (eg, X-linked adrenal hypoplasia). Abnormalities of membrane receptors for ACTH or angiotensin II may result in inadequate cortisol (eg, congenital unresponsiveness to ACTH) or aldosterone secretion, respectively. Steroidogenic defects may affect formation of cortisol (eg, CAH) or aldosterone (eg, CMO I and CMO II deficiencies due to aldosterone synthase defects). Conditions altering the availability of cholesterol for steroidogenesis may also occur (eg, ALD, adrenomyeloneuropathy [AMN]), Wolman disease, and steroid sulfatase deficiency orX-linked ichthyosis). Finally, normal adrenal glands can be damaged or destroyed by extrinsic factors (eg, bilateral adrenal hemorrhage of the newborn, adrenal hemorrhage of acute infection, and Addison disease.)

Congenital aplasia or hypoplasia of the adrenal glands.

This is a rare congenital malformation owing to a developmental disorder of the adrenal anlage. It manifests very early in life by vomiting and diarrhea with hyponatremia, hyperkalemia, and hypoglycemia. Shortly thereafter, affected children display tachycardia, hyperpyrexia, apnea, cyanosis, and eventually seizure, vascular collapse, and coma, often misdiagnosed as septicemia, intracranial hemorrhage, or other serious illness. For this reason it is often diagnosed at autopsy. Pathology often reveals small amounts of adrenal tissue either in its usual location or associated with the gonads, or scattered throughout the peritoneum. If adrenal tissue is found, the condition may be attributed to one of the other syndromes described later on.

In X-linked congenital adrenal hypoplasia (also known as adrenal hypoplasia congenita [AHC]), both cortisol and aldosterone secretions are impaired. It is described as cytomegalic adrenal hypoplasia because of the histological appearance of the adrenal cortex in patients studied at autopsy. X-linked AHC most often presents in the newborn period (1-4 weeks) with signs and symptoms of a salt-wasting crisis. However, affected patients with variable degrees of adrenocortical development may not have symptoms of adrenocortical insufficiency until later in childhood.

X-linked AHC generally occurs with hypogonadotropic hypogonadism. Mutations of DAX-1 (dosage-sensitive sex reversal adrenal hypoplasia on the X chromosome gene 1) cause combined AHC and HH in affected males. In some patients, there is a contiguous gene syndrome due to a deletion, including DAX-1 (discussed later on in the chapter), dystrophin (causing Duchenne muscular dystrophy [DMD]), and the glycerol kinase gene (causing juvenile glycerol kinase deficiency [GKD]). Patients with this complex (DMD, AHC, and GKD) also have a characteristic phenotype that may include short stature, mental retardation, testicular abnormalities (cryptorchidism, hypogonadism), and peculiar facies (drooping mouth, wide-set eyes).

Congenital defects in adrenocortical development may also be due to mutations of the SF-1 gene. This syndrome may include male to female sex reversal. Females with primary adrenal failure and SF-1 mutations have normal genitalia. Mutations of SF-1 may also lead to DSD without adrenal insufficiency.²¹

Treatment of congenital adrenal hypoplasia or aplasia consists of replacement therapy for both mineralocorticoid and glucocorticoid deficiencies (as described in detail elsewhere in the chapter).

Adrenocortical unresponsiveness to ACTH.

This disorder is caused by a genetic abnormality of the ACTH receptor (also known as the melanocortin 2 receptor [MC2R]), leading to inability of the zona fasciculata and reticularis to produce cortisol in response to ACTH stimulation. By contrast the zona glomerulosa secretes aldosterone normally. This condition is distinct from adrenal unresponsiveness to ACTH due to developmental, autoimmune, or infectious causes.

Clinically, patients present early in life with feeding problems, vomiting and failure to thrive, occasional hypoglycemia, and hyperpigmentation of the skin, as is seen in Addison disease. Laboratory evaluation reveals low glucose with normal electrolytes, low but not absent cortisol secretion, markedly elevated ACTH, and normal aldosterone secretion. There are two modes of inheritance of this disorder: X-linked recessive and autosomalrecessive. Over 30 cases of what is also known as Migeon syndrome have been reported, but some of these patients probably had a different disease. Some had sodium loss suggesting primary adrenal disease, and others presented with neurologic symptoms suggesting ALD (discussed later on in this chapter).

The association of ACTH-resistant cortisol deficiency with achalasia and absent lacrimation is known as the triple A (or Allgrove) syndrome. Patients present with hypoglycemia and severe feeding difficulties. There is also evidence of defects of both the sympathetic and the central nervous system (CNS). The defective gene in this autosomal recessive disorder is the ALADIN gene (Alacrima-Achalasia-Adrenal Insufficiency Neurologic Disorder), a member of the WD-repeat family of regulatory proteins.

Congenital adrenal hyperplasia

CAH due to deficiency of CYP21A2 (21-hydroxylase).

CYP21A2 deficiency is the most thoroughly studied and understood defect in adrenal steroidogenesis. CYP21A2 deficiency is the most common cause of disorders of steroidogenesis, and the location of its gene (CYP21A2) within the human leukocyte antigen (HLA) complex on human chromosome 6 makes it highly susceptible to mutation through recombination. The molecular basis for the majority of cases of CYP21A2 deficiency is now established, and there is correlation between severity of the clinical disorder and the effect of specific mutations on enzymatic activity. The clinical management of this disease is discussed in detail in a recent clinical practice guideline.²²

CYP21A2 deficiency is often divided into three forms, depending on the initial presentation. Two of these forms, which reflect severe deficiencies in CYP21A2 activity, present early in life. The most severe impairment in enzyme activity results in the salt-wasting form of CAH. Male patients with this form present with acute adrenal crisis in the neonatal period or early infancy, and females are usually detected at birth due to ambiguity of the external genitalia. Female patients with milder masculinization of the external genitalia but no evidence of acute adrenal crisis, or males who show signs of androgenexcess early in life, are considered to have the simple virilizing form. Identification of cases by newborn screening has blurred the distinction between these two forms, as both are detected on the newborn screen and cases are often identified before the salt-losing process is clinically significant. The screening of all neonates for CAH has been mandatory in the United States since 2008.

The nonclassic form (also called “late-onset” or “attenuated”) is typically manifested in females with evidence of androgen excess including hirsutism, amenorrhea, and infertility. In males, the mild androgen excess is typically undetectable, as the effects of testicular testosterone far outweigh the masculinizing effects of adrenal androgens. Newborn screening will detect some of these cases, which may lead to confusion about the timing and necessity of treatment.

Thus, individual patients with the various forms of CYP21A2 deficiency represent a continuum of clinical manifestations secondary to impaired adrenal production of cortisol, which reflect the spectrum of underlying genetic mutation variability.^23,24

Salt-wasting form of CYP21A2 deficiency

Pathogenesis.

A decrease in cortisol secretion reduces negative feedback at the hypothalamic-pituitary level, which leads to markedly increased secretion of CRH and ACTH, and the adrenocortical hyperplasia characteristic of the syndrome. Secretion of cortisol may be very low due to severe or even complete CYP21A2 deficiency. In addition, the adrenal cortex cannot secrete sufficient aldosterone to compensate for the salt-losing tendency created by the overproduction of 17-hydroxyprogesterone. This results in an acute adrenal or salt-wasting crisis, which will be described as follows. Simultaneously, maximal activation of the CRH-ACTH axis induces hypersecretion of adrenal androgens and near-total masculinization of the external genitalia in females.

Increased ACTH concentrations markedly increase secretion of cortisol precursors, especially the major and immediate precursor of cortisol, 17-hydroxyprogesterone (see Figure 5-3). There is also increased secretion of progesterone and 17-hydroxypregnenolone. The androgen synthetic pathway is not affected by the enzyme deficiency; thus high concentrations of available substrate, 17-hydroxyprogesterone, which would be otherwise nonphysiologic in a normal state, lead to increased androstenedione production.

The precursor, 17-hydroxyprogesterone, has limited biological activity in normal subjects. In excess, it produces sodium and water loss and potassium retention. To compensate, there is increased activity ofthe renin-angiotensin-aldosterone system, resulting in a greater amount of angiotensin II, and ultimately aldosterone, being formed. In salt-wasting CAH, marked deficiency in CYP21A2 does not permit the secretion of aldosterone. In the simple virilizing form of CAH, the partial deficiency permits increased secretion of aldosterone sufficient to maintain a normal sodium balance.

In normal subjects, the concentration of ACTH in blood is inadequate to stimulate the secretion of adrenal androgens. In CAH, ACTH hypersecretion, combined with the enzymatic block, causes an increased secretion of androgens: androstenedione, DHEA, and DHEA-S. These adrenal androgens do not bind to the androgen receptor, but androstenedione is metabolized peripherally into testosterone and accounts for the symptoms of androgen excess characteristic of CAH.

Clinical manifestations.

Increased androgen production starts early in fetal life, between 6 and 10 weeks of gestation. In the female fetus, this results in variable degrees of posterior fusion of the labia, and hypertrophy of the clitoris. The labial fusion often results in formation of a urogenital sinus located at the base of the clitorophallic structure. The degree of masculinization of the external genitalia of the female fetuses is usually classified as described by Prader (Figure 5-12). Despite the virilized appearance of the external genitalia, the uterus and fallopian tubes are normal. In the male fetus, testicular androgens carry out the normal masculinization of the external genitalia, and the addition of adrenal androgens has minimal or no effect, although penile length can be at the 95th percentile.

In female infants with salt-wasting or simple virilizing forms of CAH due to CYP21A2 deficiency, attention is attracted first to markedly ambiguous genitalia. The degree of virilization is related to severity of the enzyme defect and may be so extreme that there is complete fusion of the labia and formation of a penile urethra (Figure 5-13). In such cases, the external genitalia are those of a normal male except that no gonads are descended. The elevated secretion of ACTH is often accompanied by excess MSH; in both male and female infants, this may cause hyperpigmentation of the external genitalia.

In infants not detected presymptomatically by newborn screening, the total or almost complete absence of cortisol and aldosterone secretion results in an acute adrenal crisis usually between the 4th and 15th days of life, but occasionally as late as 6 to 12 weeks of age. Affected infants feed poorly, have vomiting and diarrhea, and lose a significant amount of weight from dehydration. Serum electrolytes show an increase in serum potassium and a fall in sodium. In the absence of treatment, acute adrenal crisis readily develops into cardiovascular collapse, cardiac arrest, and death.

Rarely, salt loss is first noted in early childhood, usually at the time of a major infection. These patients probably have a degree of CYP21A2 deficiency that is intermediate between that of the simple virilizing and salt-wasting forms. In most patients with salt-wasting CAH, the salt-losing tendency seems to be somewhat less marked after 4 or 5 years of age, and even less in late childhood and adulthood. Despite this, it has been shown that such patients cannot sustain a prolonged low-sodium diet without experiencing a major sodium and water loss. Some patients with salt-wasting CAH tolerate discontinuation of their mineralocorticoid treatment in later life, although a recent adult cross-sectional study showed a majority of classic CAH patients receiving mineralocorticoid replacement still exhibiting elevated plasma renin levels.²⁵

In poorly treated males, anabolic effects of adrenal androgens generally result in advanced somatic growth and skeletal age, enlargement of the penis, and development of pubic hair; however, the testes remain small. If a patient’s skeletal age is advanced to that of a child of pubertal age, onset of gonadotropin-mediated precocious puberty can be observed, in particular after the suppression of adrenal androgen secretion with glucocorticoid therapy. This would result in the need to treat both the CAH and the true precocious puberty.

In poorly or inadequately treated females, hypersecretion of adrenal androgens interferes with the maturation of the hypothalamic-pituitary-ovarian axis. The age at pubarche is approximately 3 years earlier than normal, thelarche occurs at a normal age, and menarche is usually delayed by 2 or more years. With complete suppression of adrenal androgen secretion, normal puberty and menstruation can ensue.

In males, hypertrophic adrenal rests may develop either in the body of the testes, near the epididymis, or in the spermatic cord, referred to as testicular adrenal rest tissue (TART). Adrenal rests are actually frequent in the normal population but are detected only when hypertrophic. These rests have been associated with infertility.²⁶ Females also may have adrenal rests, usually in the broad ligament and, on occasion, in the ovary.

Diagnosis.

In areas that have a newborn screening test for CAH, the diagnosis is often made prior to the development of clinical symptoms, especially in affected males. The screening test can also speed the diagnostic evaluation of females with ambiguous genitalia.

In areas that do not use a newborn screening test for CAH, in female infants with ambiguous external genitalia or with completely masculinized genitalia without palpable gonads, the diagnosis of the salt-wasting form of CYP21A2 deficiency is made on the basis of a normal female karyotype of 46,XX, the characteristic pattern of serum electrolytes (hyponatremic, hypochloremic, hyperkalemic acidosis), and markedly elevated plasma concentrations of plasma 17-hydroxyprogesterone and androstenedione. Because of the dehydration, there is usually a decrease in plasma volume resulting in hemoconcentration. Low plasma concentration of aldosterone along with elevated PRA confirms the primary adrenal insufficiency.

In male infants, absence of ambiguous genitalia makes the diagnosis more difficult. Clinical symptoms can be confused with those of pyloric stenosis, but the typical pattern of serum electrolytes of CAH will contrast with that of pyloric stenosis (hyponatremic, hypochloremic, hypokalemic alkalosis). The diagnosis is confirmed by demonstrating elevated concentrations of plasma 17-hydroxyprogesterone and androstenedione. Suspicion for the diagnosis is strengthened by a family history of an older sibling with CAH, or one who died in the neonatal period from a syndrome of dehydration without a specific diagnosis.

Simple virilizing form of CYP21A2 deficiency.

The pathogenesis of the simple virilizing form is similar to the salt-wasting form of CAH owing to CYP21A2 deficiency, but the incomplete CYP21A2 deficiency in the simple virilizing form allows increased ACTH activity to restore cortisol secretion to an approximately normal rate. Nevertheless, increased ACTH concentration required to normalize cortisol secretion markedly elevates production of cortisol precursors, especially 17-hydroxyprogesterone and to a lesser extent progesterone and 17-hydroxypregnenolone (see Figure 5-3). Because the androgen synthetic pathway is not affected by the enzyme deficiency, androstenedione production is high because of the ample substrate availability. As in the salt-wasting form of CAH due to CYP21A2deficiency, there is increased activity of the renin-angiotensin-aldosterone system. In the simple virilizing form, a partial deficiency permits sufficient aldosterone production to maintain normal sodium balance. Similar to the salt-wasting form, patients with the simple virilizing form have increased secretion of androgens.

Clinical manifestations.

Untreated patients with simple virilizing CAH have normal plasma cortisol concentrations and no symptoms of glucocorticoid deficiency. The salt-losing tendency caused by 17-hydroxyprogesterone is compensated by increased aldosterone levels, and electrolyte levels are normal. Hypersecretion of androgens in either sex causes early appearance of pubic hair, usually between 6 months and 2 years of age, followed by early appearance of axillary hair between 2 and 4 years of age, and facial hair between 8 and 14 years of age. Acne and deepening of the voice will also occur. Bone age and height age may become markedly advanced, and short adult stature is common in untreated or inadequately treated patients. True secondary central precocious puberty can also occur if inadequate or delayed therapy results in significant advancement of skeletal age.

Diagnosis.

Increased plasma concentrations of specific cortisol precursors (17-hydroxyprogesterone, and to alesser extent, progesterone and 17-hydroxypregnenolone) and adrenal androgens (androstenedione, DHEA, DHEA-S, and to a lesser degree, testosterone) are characteristic of CAH owing to CYP21A2 deficiency. Urinary excretion of 17-ketosteroids, the metabolites of adrenal androgens, will be markedly elevated.²⁷ Elevation of plasma concentrations of ACTH can be difficult to demonstrate. Secretion of cortisol is normal and that of aldosterone is increased in untreated patients.

In female patients, the diagnosis of simple virilizing CAH is made by the presence of ambiguous external genitalia with 46,XX karyotype and markedly increased concentrations of 17-hydroxyprogesterone and androstenedione that return to normal under glucocorticoid suppressive therapy. Ambiguous external genitalia and a 46,XX karyotype can also be seen in infants without CAH who have been masculinized either by maternal androgens (virilizing adrenal or ovarian tumor of the mother), by maternal ingestion of androgenic preparations, or by excessive gonadal secretion of androgen such as that seen in patients with 46,XX ovotesticular disorder of sex development (DSD).

In milder cases of simple virilizing CAH, masculinization of external genitalia of the newborn female can be minimal and unnoticed, and the first symptom is usually the appearance of pubic hair between 6 months and 2 years of age. The differential diagnosis includes virilizing adrenal or ovarian tumor, and premature adrenarche if the child is older. In virilizing adrenal tumors, DHEA and DHEA-S, and to a lesser degree, androstenedione are elevated, but 17-hydroxyprogesterone concentrations are normal or only slightly elevated. A dexamethasone-suppression test fails to suppress the adrenal androgens from a virilizing tumor. The diagnosis is confirmed by the finding of an adrenal mass with computed tomography (CT) or magnetic resonance imaging (MRI). In premature adrenarche, DHEA, DHEA-S, and androstenedione are increased above the low level expected in prepubertal children (but never above the concentration observed in normal adults), and 17-hydroxyprogesterone levels are normal. In children with early pubarche, exposure to exogenous androgen, such as contact with the skin of a person using a topical testosterone preparation, should be considered.

In male infants, the diagnosis of simple virilizing CYP21A2 deficiency is not clinically apparent. If not detected by a newborn screen for CAH, the diagnosis should be considered when a child presents with premature appearance of pubic hair and advanced bone and height ages, and testes that are prepubertal in size. The diagnosis of CAH is confirmed by high plasma concentrations of 17-hydroxyprogesterone and androstenedione. The differential diagnosis of early pubic hair in a boy includes a number of possibilities, of which CAH is only one. Central precocious puberty of idiopathic origin and a benign or malignant gonadal or adrenal tumor may cause early pubic hair development. In central precocious puberty, the androgen responsible for the masculinization is testosterone; on the other hand, the concentrations of androstenedione, DHEA, and DHEA-S are only slightly elevated above the prepubertal concentration but not higher than the values found in normal adults. Also in central precocious puberty (gonadotropin-mediated), the testes enlarge as opposed to the small testes typical of CAH. Early pubic hair development can also be related to a human chorionic gonadotropin-producing tumor such as a dysgerminoma or hepatoma, to a testosterone-secreting unilateral Leydig-cell tumor, or to a virilizing adrenal tumor. Leydig-cell tumors usually can be palpated in one of the testes; a sonogram ofthe scrotum confirms the presence of the lesion. Leydig-cell tumors produce mainly testosterone, in contrast to virilizing adrenal tumors, which produce DHEA-S and DHEA. As mentioned previously, exposure to exogenous androgen as a cause of early virilization should also be considered.

Nonclassic form of CYP21A2 deficiency: pathogenesis.

This form of CAH represents the mildest degree of CYP21A2 deficiency. Because the symptoms in the female appear at puberty or later, the terminology “late-onset” or “attenuated” has also been used. The term “nonclassic CAH” (NC-CAH) has been proposed to contrast with the “classic forms” (simple virilizing and salt-wasting). There also exists an asymptomatic or cryptic form of CYP21A2 deficiency manifested by the steroid pattern diagnostic of CAH in the complete absence of symptoms of the disorder.²⁸ Minimal CYP21A2 deficiency causes less change in steroidogenesis and attenuation of the symptoms of the disorder. Absence of masculinization of the female genitalia during fetal life and little or no signs of androgen effects during childhood reflect the low degree of fetal adrenal androgen secretion.

Clinical manifestations.

There are essentially no symptoms of NC-CAH in males, since at puberty the testicular secretion of testosterone overrides the effects of increased adrenal androgen output. In females, hirsutism and (occasionally) virilization that occur at puberty appear to result from excessive response of adrenal androgens with adrenarche. Most affected girls have normal breast development, but androgen excess causes either primary or secondary amenorrhea and, in some patients, multiple small ovarian cysts.

Diagnosis.

In female patients of pubertal age, baseline concentrations of plasma 17-hydroxyprogesterone, androstenedione, and, oftentimes, testosterone are elevated. In patients who have only moderately elevated basal concentrations of these steroids, in whom the diagnosis is not clear, administration of IV ACTH (250 μg) may be useful. Affected patients will have exaggerated increases in 17-hydroxyprogesterone (> 1200 ng/dL). An unstimulated level of 17-hydroxyprogesterone has been suggested as a screening tool (170-300 ng/dL cutoffs have been used) obtained in the morning and the follicular phase.²⁹ PCOS, also called Stein-Leventhal syndrome, is a primarily ovarian androgen excess disorder presenting with typical symptoms (hirsutism, acne, menstrual abnormalities) that are similar to those found in NC-CAH. However, PCOS is more common than NC-CAH, the latter being present in fewer than 10% of women with hirsutism and menstrual irregularities. In both PCOS and NC-CAH, androgen effects can also include slight enlargement of the clitoris, some increase in muscle mass, and deepening of the voice. The IV ACTH test may be the best means to distinguish the two conditions, although in PCOS, the increase in stimulated 17-hydroxyprogesterone levels is either normal or slightly increased (similar to that of heterozygous carriers for CAH), in contrast to the markedly abnormal levels seen in NC-CAH. Differentiating NC-CAH and PCOS could be complicated by ovarian cysts found in both conditions, and that patients with both conditions may respond to glucocorticoid-suppressive treatment.^30,31

In PCOS, high insulin levels act on the ovary with LH to increase testosterone production by the thecal cell. Insulin has been shown to increase adrenal steroidogenesis by increasing 17a-hydroxylase and 17,20-lyase activities.³² However, hyperandrogenism may itself lead to insulin resistance,³³ which may contribute to irregular menses in women with NC-CAH and PCOS.³⁴

Long-term clinical issues and outcomes in CAH.

Results of long-term treatment of CAH reveal numerous unresolved clinical issues in the adult CAH population, including attainment of predicted adult height, fertility, bone mineral density, and cardiovascular disease risk.³⁵ In addition, longer-acting glucocorticoids (prednisone, dexamethasone) are commonly used in the management of adults,^35,36 and treatment goals differ from those for children with CAH.²⁵

Adult height in CAH patients is significantly below the normal population, with a mean adult height SDS of –1.0 ± 1.1 for classic patients, and –0.4 ± 0.9 for NC-CAH patients.^23,36 Diagnosis at a later age correlates with reduction in final adult height. In terms of quality of life, adults in the United Kingdom self-reported that the significantly reduced final adult height had a lesser impact than obesity or compromised sexual activity.³⁶

Adult males with CAH can have significantly lower concentrations of serum LH, although they are fertile by sperm count and reproductive history. Infertility has been described,³⁷ with TART present in almost the majority of adult males (44%-69%) and having a significant impact on fertility.^23,36 For this reason, regular testicular examinations and routine testicular ultrasounds are recommended for sexually mature males with CAH as early as adolescence.²²

Adult females.

Adult female patients with salt-wasting CAH tend to have more severe problems related to genital surgery and infertility than those with the simple virilizing form. Decreased sexual activity and pregnancies are reported in adult women with the salt-wasting form,²³ along with pain during intercourse and fewer women with classic CAH seeking pregnancy compared to NC-CAH patients.³⁶ In addition, among women with CAH who become pregnant, there are increased risk of gestational diabetes and an unexplained reduction in the number of male infants born (26% males vs 56% in controls).³⁸

For both adult men and women with CAH, long-term glucocorticoid therapy can also contribute to increased fat mass and elevated plasma lipid levels.

Adrenal medullary deficiency.

This deficiency has also been shown in patients with severe CAH, manifested by subnormal epinephrine and glucose response to moderate- and high-intensity exercise. Cortisol produced by the adrenal cortex is necessary for the proper formation of the adrenal medulla.³⁹ The degree of severity of epinephrine deficiency is correlated with severity of CAH.^39,40 Epinephrine deficiency is not known to be causative of serious medical complications in these patients. Although as a counter-regulatory hormone, it could contribute to hypoglycemia during acute illness in these patients.⁴¹

Genetic aspects of CYP21A2 deficiency.

CYP21A2 deficiency is a monogenic disorder inherited as an autosomal recessive trait and is expressed clinically only in homozygous subjects. There is tight linkage between CYP21A2 deficiency and the HLA locus within the major histocompatibility complex (MHC) on chromosome 6 between the genes of the class III products of the MHC and the complement C4 genes. CYP21A2 is located within a region of high gene density and frequentrecombination events called the RCCX module, along with the gene encoding tenascin-X (TNXB), C4, and RP. Isolation of the cytochrome P450 protein having CYP21A2 activity led to the cloning and sequencing of the duplicated CYP21A2 gene and CYP21A1P pseudogene (Figure 5-14). The extended haplotype HLA-A3,Bw47,C6,DR7, GLO1/BfF,C2C,C4A1,C4BQO (so-called HLA-Bw47) was found to be linked to a large deletion including one of the CYP21A2 genes and one of the C4 genes; the remaining CYP21A2 gene was inactive and was the precursor of the CAH-linked HLA-Bw47 haplotype.

In the nonclassic form of CYP21A2 deficiency, a genetic linkage disequilibrium occurs with the HLA-B14,DR1 haplotype. This haplotype includes three complement C4 genes (C4A2, C4B1, C4B2) in tandem with three CYP21A2 genes, two of them being pseudogenes and one being a CYP21A2 gene with a missense mutation in exon 7 (P281L). There is a contiguous gene syndrome involving CYP21A2 and TNXB, termed CAH-X syndrome. TNXB haploinsufficiency is present in 7% of patients with CAH due to CYP21A2 deficiency, and clinical features of Ehlers-Danlos syndrome are found in almost all patients characterized with the CAH-X syndrome.⁴²

Frequency of CYP21A2 mutations in the general population.

Comparing the number of clinically diagnosed cases to the population base underestimates the frequency owing to deaths and unrecognized cases. Using the newborn screen to estimate frequency overestimates cases due to false positives. Various surveys in Europe and North America reported an incidence of the disorder ranging from 1 in 10,000 to 1 in 25,000 births, giving a frequency of carriers for the mutant gene of 1:50 to 1:80. The incidence of CAH found in various newborn screenings shows incidences between 1:10,000 and 1:18,000. Much higher incidences are found in inbred populations such as the Yupik Eskimo of Alaska (1:490 case survey, 1:684 by screening) and in the island of La Reunion in the Indian Ocean (1 in 2000 births). The frequency of nonclassic CYP21A2 deficiency is even more difficult to determine in view of the frequent complaint of hirsutism and virilism in female subjects.

Types of mutations of the CYP21A2 gene.

The presence of highly homologous, tandemly arranged genes in the RCCX region on chromosome 6p (see Figure 5-14A) leads to meiotic mispairing and unequal crossing over. This leads to gene duplication in one chromatid and deletion in the other (see Figure 5-14A). Abnormal numbers of CYP21A2 and CYP21A1P genes are found frequently both in the normal population and in patients with CYP21A2 deficiency. Deletion events may account for approximately 20% to 25% of all CYP21A2-deficient chromosomes. Of these, the most frequent is deletion of a 30-kb region that includes the 3′ portion of CYP21A1P, all of C4B, and the 5′ end of CYP21A2. The 5′ end of the fusion gene contains sequences derived from CYP21A1P, which include deleterious mutations that preclude enzymatic activity of the product may be owing to a previously undescribed large gene tandem deletion.

Gene conversion events, another mechanism that frequently produces CYP21A2 mutations, involve a nonreciprocal exchange of homologous genetic information; the sequence of one gene (the target) is “converted” to that of a related gene (the source). Gene conversion events probably involve incorrect meiotic alignment of the two CYP21A2 genes followed by mismatch repair converting a segment of the sequence of the CYP21A2 to that of the CYP21A1P pseudogene. The net result of such gene conversion events is the transfer of deleterious mutations from CYP21A1P to CYP21A2, and the formation of a chimeric CYP21A1P/CYP21A2 gene.⁴³ These small gene conversions generate the full spectrum of clinical phenotypes of CYP21A2 deficiency, accountingfor most mutations that alter the enzymatic activity of the CYP21A2 product. The most common point mutation of CYP21A2 is in intron 2 and is the presumed cause of CAH in the Yupik Eskimos. It occurs normally in the CYP21A1P gene and alters splicing. Genotype-phenotype correlations have been useful in the classification of patients at the time of diagnosis and have been validated with long-term follow-up.

In some patients, the C4B/CYP21A2 tandem appears to be replaced by a C4A/CYP21A1P tandem, a so-called large gene conversion. This accounts for up to 15% of mutations in the salt-wasting form and may have arisen as a result of two unequal crossing-over events.

Rarely, de novo point mutations and mutations that were not transferred from CYP21A1P occur in CYP21A2 deficiency, and they are associated with salt-wasting and non–salt-wasting forms.

Targeted mutational analysis for CYP21A2 is commonly available in commercial laboratories. However, mutations not detected by this multiplex PCR method require further gene sequencing to determine the genotype of the patient with CAH.⁴⁴

Detection of heterozygotes for the CAH trait.

Determination of carrier status by hormonal testing was first performed using obligate CAH heterozygotes (parents of patients). Carriers showed normal basal concentrations of steroids but elevated cortisol precursors (17-hydroxyprogesterone, progesterone) in response to ACTH stimulation. Because the ovaries produce 17-hydroxyprogesterone and progesterone late in the menstrual cycle, it is necessary to perform the tests of adult females during the early follicular phase. Using a 30-minute test, an additive rate of increase in progesterone plus 17-hydroxyprogesterone that is less than 7 ng/dL/min is found in patients who have two normal CYP21A2 genes. Values of 9 to 30 ng/dL/min are found in heterozygotes for CAH. However, there is a 5% to 10% overlap between normals and carriers, and genotyping appears superior to determine carrier status in families where the genotype of the index case is known.⁴⁵

CAH prenatal considerations

Prenatal diagnosis of CYP21A2 deficiency.

This diagnosis can be accomplished when an index case has already been studied and the genotype is known, via a biopsy of chorionic villi obtained during the first trimester. Chorionic villi sampling can be used for karyotyping, characterization of CYP21A2 mutations, and HLA typing if needed for verification. Sources of error can arise from recombination in the HLA locus, possibility of contamination of the fetal material by maternal tissue, and generation of unauthentic sequences by the PCR amplification used for the genotyping. Amniocentesis can also yield cells for karyotyping, CYP21A2 genotyping, and HLA typing, and the fluid permits measurement of steroid concentrations. Steroid levels can only be interpreted accurately if the mother is not receiving prenatal dexamethasone treatment (see in the section Prenatal Therapy of CYP21A2 Deficiency). In affected fetuses the levels of 17-hydroxyprogesterone and androstenedione are markedly elevated; the concentration of cortisol, progesterone, DHEA, and DHEA-S show no significant abnormalities.⁴⁶

Prenatal therapy of CYP21A2 deficiency.

Prenatal glucocorticoid therapy has been used to reduce masculinization of the genitalia and exposure of the brain to androgens in affected female fetuses. However, the long-term effects of this therapy remain to be seen, in both treated fetuses with CAH and treated nonaffected fetuses, and the current guidelines do not include prenatal dexamethasone therapy as part of standard of care.²²

Because cortisol does not cross the placenta readily, dexamethasone at a dose of 20 μg/kg of body weight/24 h (usually 1-1.5 mg/day) is used for this treatment. To prevent masculinization of the external genitalia between 5 and 12 weeks of gestation, preservation of normal female external genitalia of affected females requires treatment initiation at 5 to 6 weeks.⁴⁶ Treatment is monitored by study of the suppression of maternal plasma cortisol or urinary free cortisol. Suppression of fetal adrenal activity can also be documented by suppression of estriol in maternal plasma and maternal urine.

Because the chances of heterozygous parents having an affected child is one in four, and half the fetuses will be male, the risk of an affected female fetus is one in eight, or only 12.5%. Therefore, dexamethasone therapy is given unnecessarily in 87.5% of pregnancies, initiated prior to prenatal testing. Attempts to decrease the length of unnecessary therapy are made by prenatal karyotype and diagnosis of CAH, with discontinuation of treatment in all male fetuses, heterozygous females, and homozygous normal females. Maternal side effects of therapy include excessive weight gain, fluid retention, and hypertension. The potential advantages of treatment may outweigh the possible risk of side effects for affected infants, but informed consent for this treatment must include the fact that long-term studies have not verified its safety, with regards to cognitive function in prenatally treated children who were at risk for CAH. Verbal working memory has been noted to be impaired in follow-up studies of CAH-unaffected children exposed as fetuses.⁴⁷ It is recommended by many that this treatment only be performed in centers with expertise and experience in this area, as part of an institutional review board ethically approved protocol, ideally with longitudinal follow-up.²² This could include follow-up of all treated individuals. A multidisciplinary team approach to prenatal care that includes a perinatologist would be the ideal approach.⁴⁸

Neonatal screening.

Neonatal screening for CAH by determination of 17-hydroxyprogesterone concentrations on filter paper blood spots was developed to allow diagnosis and treatment prior to life-threatening adrenal crisis. Because females with salt-wasting CAH should attract attention because of their ambiguous genitalia, the major benefit has been the identification and preventative treatment of affected males. Pitfalls include false positives in premature infants, false negatives (particularly in females), and difficulty in differentiating the salt-wasting and non–salt-wasting forms in affected patients. Complementing the traditional enzyme immunoassay screening test for 17-hydroxyprogesterone with a second screen using liquid chromatography-tandem mass spectrometry for steroid profiling (eg, 17-OHP, 11-deoxycortisol, 21-deoxycortisol, cortisol, androstenedione) could increase the specificity of the screening process and decrease false positives.⁴⁹ There is also genotyping in presumptive positive cases, and gene analysis on dried blood spots.^50,51 These additional measures have been helpful in some situations, especially in the evaluation of infants who are premature and/or critically ill.

Other forms of CAH

CAH due to deficiency of CYP11B1.

Steroid CYP11B1 (11β-hydroxylase) deficiency, a hypertensive form of CAH, accounts for approximately 5% of all cases of CAH. In the zona fasciculata, CYP11B1 deficiency impairs cortisol and corticosterone secretion. Compensatory ACTH release increases the production of the steroid precursors 11-deoxycortisol, DOC, and 18-hydroxy DOC. Secretions of 17-hydroxyprogesterone and progesterone are also increased, but to a lesser extent than in CYP21A2 deficiency. CYP11B1 deficiency, like CYP21A2 deficiency, is characterized by masculinization of the female fetus and by postnatal virilization. Affected females almost always show ambiguity of the external genitalia at birth but rarely virilize only during puberty or adulthood in a late-onset form of the disease. Male newborns have normal external genitalia with descended testes. Gynecomastia can also develop prior to puberty in untreated subjects. As with CYP21A2 deficiency, nodules of hyperplastic ectopic adrenal tissue can develop in the spermatic cord, epididymis, or testes. In both sexes, hypertension—with suppressed renin, angiotensin, and aldosterone levels—can result from the increased secretion of DOC, a mineralocorticoid. Elevations in blood pressure are usually moderate but can occasionally be sufficiently severe to cause cardiomegaly and eventual cardiac failure. Thus, this disorder is a genetic cause of low renin hypertension.

Diagnosis.

CYP11B1 deficiency may be detected by the CAH newborn screening test. As for CYP11A2 deficiency, this is particularly true for male infants who have normal genitalia. In CYP11B1 deficiency, the 17-hydroxyprogesterone level tends to be elevated to a detectable degree. Distinction of the diagnosis from CYP21A2 deficiency is accomplished by detecting increased levels of DOC and 11-deoxycortisol in blood. In addition, patients with CYP11B1 do not have evidence of salt wasting. Prenatal diagnosis of CYP11B1 deficiency is now available, based on measurement of maternal urinary tetrahydro-11-deoxycortisol. This is of greatest benefit in populations at risk, such as Jews of Moroccan origin.

Genetics.

CYP11B1 deficiency is an autosomal recessive disorder. A gene encoding CYP11B1 has been cloned and maps to chromosome 8q21-q22, a finding consistent with the functional and anatomical segregation of the CYP11B1 isozymes discussed as follows.

Two homologous adjacent CYP11B1 genes, designated CYP11B1 and CYP11B2, encode two distinct proteins (Figure 5-15). Although the two genes have 93% identity in their predicted amino acid sequences, they differ in sites of expression and in the enzymatic activities of their protein products. The product of the CYP11B1 gene, termed “11β-hydroxylase,” is expressed at high levels in the zonae fasciculata/reticularis where it converts 11-deoxycortisol (compound S) to cortisol. In the zona glomerulosa it mediates 11β-hydroxylation conversion of DOC to corticosterone but does not perform the terminal reactions required for aldosterone biosynthesis. The other gene, CYP11B2, encodes aldosterone synthase in the zona glomerulosa, catalyzing all reactions needed for the conversion of DOC to aldosterone (11β-hydroxylation, 18-hydroxylation, and 18-dehydrogenation; Figure 5-16). Nonsense mutations, missense mutations, small insertions and deletions, as well as a 5-bp duplication causing CYP11B1 deficiency have been identified. The duplicated CYP11B1/CYP11B2 gene arrangement confers a predilection for unequal crossing over and gene deletion, but this occurs much less frequently than in CYP21A2 deficiency.

CAH due to deficiency of CYP17A1

Pathophysiology and clinical manifestations.

Steroid CYP17A1 (17α-hydroxylase) catalyzes both CYP17A1 and 17,20-lyase reactions, and it is expressed both in the adrenal cortex and in the gonad. Deficiencies of both activities are more common than isolated deficiency of 17,20-lyase; of more than 120 patients reported, approximately 14 exhibited only 17,20-lyase deficiency. As with other forms of CAH, clinical manifestations result from disrupted glucocorticoid production and compensatory increase in ACTH secretion. In patients with CYP17A1 deficiency, ACTH stimulation leads to high levels of corticosterone (which binds with low affinity to the GR) and DOC (see Figure 5-3), causing hypertension. Although the biochemical pathways for aldosterone production in the zona glomerulosa are intact, the presence of high circulating concentrations of DOC suppress the renin-angiotensin system, thus leading to decreased aldosterone levels and low renin hypertension.

Deficiency of 17,20-lyase causes inability to form androgens and estrogens. Affected males present with ambiguous external genitalia or in some cases with completely female-appearing genitalia. Müllerian regression occurs normally, as production of testicular müllerian inhibiting factor is not affected by the CYP17A1 deficiency. The external genitalia of affected females are normal at birth. In both females and males, inability to produce sex steroids becomes apparent at the normal time of puberty. Female patients usually present with primary amenorrhea and lack of breast development due to estrogen deficiency and scant or absent axillary and pubic hair due to adrenal androgen deficiency. Males demonstrate failure of masculinization at puberty.

Diagnosis.

Increased levels of pregnenolone, progesterone, DOC, 18-hydroxy-DOC, and corticosterone are characteristic. Because of increased DOC, 18-hydroxy-DOC, and corticosterone, renin and aldosterone levels are suppressed. From 3 to 4 months of age until puberty, plasma concentrations of 17-hydroxyprogesterone, 17-hydroxypregnenolone, androgens (DHEA, DHEA-S, androstenedione, testosterone), and estrogens (estradiol) are normally low; thus, demonstration of decreased concentrations in patients with CYP17A1 deficiency is not always possible.

Steroid patterns so far described apply to patients with combined CYP17A1 and 17,20-lyase deficiencies. In rare patients with isolated 17,20-lyase deficiency, gonadal steroid deficiencies in adolescence occur, but increased 17-hydroxyprogesterone and 17-hydroxypregnenolone concentration maintains normal cortisol and aldosterone secretion, and levels of corticosterone and DOC are approximately normal.

In newborn patients with 46,XY karyotype and ambiguous genitalia, measurement of cortisol and androgen precursors elucidate the enzymatic defect. The diagnosis may be missed in infants with completely female-appearing genitalia whether the karyotype is 46,XX or 46,XY. At the age when puberty is expected, CYP17A1 deficiency will be detected because of elevated gonadotropin levels, low gonadal steroid concentrations, elevated levels of precursors, and low renin hypertension.

Genetics.

The gene encoding 17α-hydroxylase, CYP17A1, has been cloned and mapped to chromosome 10q24.3. In contrast to CYP21A2 deficiency, large-scale deletions are not an important cause of CYP17A1 deficiency. Rather, deleterious mutations include missense and nonsense mutations as well as small insertions or deletions that alter the reading frame or splice sites responsible for loss of 17-hydroxylase activity as well as17,20-lyase deficiency.⁵² In a reanalysis of a Swiss family described in 1972 as having isolated deficiency of 17,20-lyase activity, a novel molecular mechanism was identified. The affected 46,XY individuals who had undervirilization were shown to have mutations impacting the activity of the enzymes AKR1C2 and AKR1C4 within the alternative pathway of androgen biosynthesis.⁶

CAH due to deficiency of 3β-HSD2

Pathogenesis and clinical manifestations.

CAH due to 3β-HSD2 deficiency represents fewer than 1% of all CAH cases. In severe 3β-HSD deficiency there is near absence of secretion of biologically active glucocorticoids, mineralocorticoids, and androgens. The only accumulated precursors prior to the enzymatic blocks are pregnenolone and DHEA and several of their metabolites (see Figure 5-3). Mapping of a gene encoding 3β-HSD2 to chromosome 1 confirmed the clinical observation that it was an autosomal recessive trait.

In patients with severe deficiency, ambiguous genitalia and evidence of salt loss are present. The main androgens secreted in this form of CAH are DHEA and its 16-hydroxylated derivative. Neither binds to the androgen receptor, and thus neither has biological activity. Nevertheless, newborn females with severe 3β-HSD2 deficiency exhibit androgenic effects (slight labial fusion and clitoral enlargement), suggesting that some biologically active androgens are produced. On the other hand, there is inadequate androgen production to result in complete masculinization of the genitalia in males. As with CYP21A2 deficiency, impaired corticosteroid production leads to signs and symptoms of adrenal insufficiency that may be fatal if left untreated in the neonatal period. Patients with less severe defects produce sufficient mineralocorticoid to avoid salt-wasting crises. 3β-HSD2 deficiency also prevents gonadal steroidogenesis, which contributes to abnormal genital development described previously. Analysis of steroid profiles, particularly following ACTH infusion, suggest that a mild defect in 3β-HSD activity could cause hirsutism, oligomenorrhea, or infertility in older females. However, studies of various isoforms of 3β-HSD2 in these patients have not revealed mutations, and recent studies indicate that this hormonal phenotype is more likely a variant of insulin-resistant PCOS.^53,54

Diagnosis.

Deficiency of 3β-HSD2 may be diagnosed by demonstrating elevated serum levels of pregnenolone, 17-hydroxypregnenolone, DHEA, and DHEA-S. Normal newborn infants normally secrete relatively high amounts of DHEA, DHEA-S, and pregnenolone and its metabolites. Thus, it may be challenging to clearly establish the diagnosis in cases of milder 3β-HSD2 deficiency.

Genetics.

Two distinct human genes that encode isozymes of 3β-HSD, designated types 1 and 2, map to chromosome 1p13. Although the products of these two genes differ slightly in the kinetics with which they metabolize steroids, both forms have similar enzyme activities in the production of glucocorticoids and androgens. However, only the type 2 gene is expressed in typical steroidogenic tissues (adrenal and gonads), whereas the type 1 gene is expressed predominantly in placenta, skin, and mammary tissue.

The molecular defects in the type 2 3β-HSD2 gene (HSD3B2) responsible for salt-wasting CAH are nonsense and frameshift mutations, and structure-function relationships of HSD3B2 gene mutations in both the salt-wasting and non–salt-wasting forms have been determined.

Congenital lipoid adrenal hyperplasia (StAR deficiency, CYP11A1 deficiency)

Pathogenesis, clinical manifestations, and diagnosis.

The underlying defect in the rare disorder of lipoid CAH is an inability to convert cholesterol to pregnenolone, preventing the biosynthesis of all major steroid classes. Because of a failure to produce androgens in utero, genetic males present with normal-appearing female external genitalia; because of unimpaired production of MIS, the internal ducts develop along male patterns. Females have normal-appearing genitalia at birth. Glucocorticoid and mineralocorticoid deficiency leads to symptoms and signs of adrenocortical insufficiency and salt loss. In contrast to patients with salt-wasting CYP21A2 deficiency, the age of presentation varies and patients may not be diagnosed until several months of age. Moreover, there are reports of genetic females (46,XX) with lipoid CAH who, at the time of puberty, underwent menarche, indicating capacity for gonadal steroidogenesis.⁵⁵

The adrenal glands in these patients show marked hyperplasia, with cortical cells engorged with lipoid material. This histologic picture and the failure to produce significant amounts of any steroids led to the hypothesis that congenital lipoid adrenal hyperplasia results from a mutation in CYP11A1, the gene encoding the enzyme required three steps to convert cholesterol to pregnenolone. However, most cases of lipoid CAH result from mutations in steroidogenic acute regulatory protein (StAR), required for cholesterol delivery to the mitochondria where CYP11A1 acts.

Genetics.

The StAR gene maps to chromosome 8p11.2. StAR gene mutations causing lipoid CAH include frameshift, nonsense, missense, and splicing mutations that interfere with StAR activity. As StAR is expressed in the adrenal cortex and gonad, but not in the placenta or brain, patients with StAR mutations can have placental and gonadal pregnenolone synthesis. This explains why patients with lipoid CAH survive gestation as the placenta has active steroidogenesis without StAR, and some patients with lipoid CAH have gonadal steroid synthesis at the time of puberty.

CYP11A1 maps to chromosome 15q23-q24. It has been proposed that mutations in CYP11A1 are incompatible with fetal survival in utero, and that occasional cases of recurrent miscarriage may result from mutations of CYP11A1 that preclude placental steroidogenesis. However, a number of patients with CYP11A1 deficiency as a result of CYP11A1 gene mutations have now been described.

Cytochrome P450 oxidoreductase (POR)deficiency.

POR deficiency is rare and is caused by mutations in the POR gene encoding P450 oxidoreductase (an enzyme that transfers electrons to cytochrome P450 of CYP21A2 and CYP17A1). This results in partial deficiencies of the enzymes 21-hydroxylase, aromatase, and 17α-hydroxylase, with the 17,20-lyase activity of P450c17 the most disrupted.⁵⁶ Most patients have genital anomalies at birth, with features of a skeletal dysplasia known as Antley-Bixler syndrome, and partial deficiencies of P450c17 and P450c21 activity. It affects differentiation of genitalia in both males and females, owing to decreased 17,20-lyase activity in males. In females, it is less clear, but partial virilization could be secondary to diminished aromatase activity or overproduction of 17-hydroxyprogesterone leading to the “backdoor” pathway of androgen synthesis (DHT) in certain patients.⁵⁷

Other causes of inborn adrenal insufficiency

Adrenoleukodystrophy (Siemerling-Creutzfeldt disease; Schilder disease).

Adrenoleukodystrophy (ALD), adrenomyeloneuropathy (AMN), and closely related variants are peroxisomal disorders that affect the CNS, adrenal cortex, and at times other organs. The biochemical abnormality common to all forms is elevated plasma and tissue concentrations of very-long-chain fatty acids (VLCFA), which accumulate due defects that inhibit their normal breakdown in the peroxisome.

In ALD, there is nearly constant occurrence of adrenocortical failure concomitant with the irreversible degenerative neurologic defects seen in these patients. Adrenal failure may predate, occur simultaneously with, or follow the onset of the neurologic deterioration. The observation that patients thought to have Addison disease were later shown to have ALD or AMN underscores the need to measure plasma VLCFA concentrations in all male patients with primary adrenal failure of unknown etiology.

X-linked ALD/AMN.

There are several different phenotypes in X-linked ALD, and more than one phenotype may exist within a family. Childhood ALD was the first type described and is believed to be the most common. These boys develop normally in early childhood but then develop progressive neurologic disability by about age 7 years (range 2.75-10 years). Neurologic deterioration progresses rapidly, often leading to the bedridden state within 2 years. Adolescent ALD occurs in boys whose illness presents between the ages of 10 and21 years. The symptoms resemble those of childhood ALD, but the rate of neurologic deterioration may be slower. AMN occurs in men whose neurologic symptoms begin after the age of 21 years. The rate of neurologic deterioration is fairly slow, over 5 to 20 years. Primary gonadal failure is common among these patients, as it is in other forms of X-linked ALD. Adult cerebral ALD presents in men after the age of 21 years with cerebral neurologic defects such as dementia, seizures, or behavioral disturbances. Addison-only form of ALD occurs in approximately 10% of patients with adrenal failure and no symptoms of neurologic deterioration. They are not recognized as having AMN because the time between the onset of adrenal failure and the onset of neurologic abnormalities may be decades. Asymptomatic ALD has been detected in some 100 individuals. These individuals have the biochemical abnormalities of ALD but none of the clinical features. Symptomatic heterozygotes: Approximately 200 heterozygote women have been identified with a clinical picture similar to AMN, but the onset occurs later (∼40 years of age) with a slower rate of progression, adrenocortical insufficiency being rare.

Neonatal (autosomal recessive) ALD.

In this form, neurologic abnormalities and adrenocortical insufficiency occur in the prenatal or neonatal period (ie, not preceded by a period of normal development typical for X-linked ALD). It is an autosomal recessive disorder of peroxisomes in which VLCFA accumulate, as in X-linked ALD, but the biochemical defect is more extensive than in X-linked ALD and more organ systems are generally involved. Neonatal ALD is similar to but less severe than the cerebrohepatorenal syndrome of Zellweger, in which peroxisomes are totally absent. An intermediate severity form of ALD exists, known as Refsum disease.

Genetics of ALD.

The Xq28 gene that is defective in X-linked ALD prevents normal functioning of a peroxisomal membrane protein with an ATP-binding motif, ABC (ATP-Binding Cassette) protein, involved in the transfer of VLCFA CoA synthase into the peroxisomal membrane. Mutations of this gene found in patients with ALD include missense, nonsense, frameshift, and splice site defects.

In the autosomal recessive forms of ALD (eg,Zellweger syndrome, neonatal ALD, and infantile Refsum disease), defects in a gene required for peroxisomal biosynthesis, PEX1, are common. Other patients withZellweger syndrome have mutations in the gene encoding the 70K peroxisomal membrane protein (PMP70).

Acid lipase deficiency (Wolman disease).

Wolman disease is an autosomal recessive disorder caused by deficiency of lysosomal acid lipase, an enzyme that catalyzes the hydrolysis of cholesterol esters and triglyceride and frees cholesterol from its esters in order to make it available for steroidogenesis. Patients develop massive accumulation of esterified lipids, which produces multisystem failure at an early age. Over 50 cases of this disease have been reported. Patients generally present within the first weeks of life with failure to thrive, vomiting, abdominal distention, and jaundice. They have anemia, hepatosplenomegaly, steatorrhea, calcified enlarged adrenal glands, and signs and symptoms of adrenal insufficiency. Blunted adrenocortical response to ACTH has been described. This is a rapidly progressive, untreatable disease, which usually results in death by 6 months of age. The diagnosis is made by demonstration of deficient cellular activity of acid lipase, usually in cultured skin fibroblasts or lymphocytes. Serum lipid profiles are characteristically normal. Storage of cholesterol esters and triglycerides occurs and produces foam cells in the liver, adrenal cortex, spleen, intestine, lymph nodes, circulating leukocytes, bone marrow, and CNS.

The gene encoding acid lipase, which is defective in lysosomal acid lipase deficiency, maps to chromosome 10. An allelic variant of Wolman disease, cholesterol ester storage disease, is a milder form of the disorder. The age of onset is later, the course is less rapidly progressive, and the adrenal glands are rarely calcified. However, hyperbetalipoproteinemia is common, and severe premature atherosclerosis may occur.

Steroid sulfatase deficiency (X-linked ichthyosis).

Steroid sulfatase (STS) deficiency is an X-linked recessive disorder of steroid metabolism in which the major clinical manifestation is ichthyosis. The enzyme deficiency results in accumulation of DHEA-S and cholesterol sulfate. It is believed that ichthyosis occurs because of cholesterol sulfate accumulation in the skin, and its interference with epidermal cohesion. The altered steroid metabolism does not produce adrenal insufficiency but may erroneously suggest fetal adrenal insufficiency because of low maternal estriol levels.

Smith-Lemli-Opitz syndrome.

Smith-Lemli-Opitz syndrome is an autosomal recessive disorder of cholesterol biosynthesis caused by mutations in 7-dehydrocholesterol reductase, an enzyme required to convert 7-dehydrocholesterol to cholesterol. The syndrome includes microcephaly, facial typical features, and syndactyly. Affected males have either ambiguous genitalia or nearly normal female external genitalia. Adrenal insufficiency is not universal, but in some patients the adrenal insufficiency is marked enough that patients have presented with mineralocorticoid deficiency.⁵⁸

Defects in aldosterone production.

Isolated defects in the steroidogenesis of mineralocorticoids do not cause the hyperplasia of the adrenal glands as seen with deficient glucocorticoid biosynthesis and compensatory elevated ACTH secretion. There are three major genetic disorders of mineralocorticoid biosynthesis. Deficiencies in the gene product of CYP11B2 are associated with two of these disorders. A third genetic disorder of this locus is a rare form of autosomal dominant hypertension caused by a hybrid CYP11B1/CYP11B2 gene.

Defects in aldosterone synthase.

A genetic defect in the CYP11B2 gene impairs the production of mineralocorticoids without compromising glucocorticoid production. CYP11B2 carries out both 18-hydroxylase and 18-dehydrogenase reactions. Deficiencies of these two activities are clinically distinct—CMO I or 18-hydroxylase deficiency and CMO II or 18-dehydrogenase deficiency (see Figure 5-16). In the zona glomerulosa, CYP11B2 also catalyzes the 11β-hydroxylation required for aldosterone production. As discussed previously, the 11-hydroxylation reaction in the glucocorticoid pathway is catalyzed by CYP11B1, which is stimulated by ACTH.

Pathophysiology, clinical features, and diagnosis.

Deficiency of CMO I or CMO II causes aldosterone deficiency and elevated renin, accompanied by accumulation of steroid precursors prior to the biosynthetic block: DOC and corticosterone in CMO I deficiency; DOC, corticosterone, and 18-hydroxycorticosterone in CMO II deficiency (see Figure 5-16). As these precursors possess some mineralocorticoid activity, patients with CMO I or CMO II deficiency generally present with partial salt loss, rather than the typical salt-wasting crisis of complete mineralocorticoid deficiency. Infants may present only with failure to thrive.

18-Hydroxylase (CMO I) deficiency.

Renal salt wasting and decreased growth velocity develop in thesechildren. Postmortem histopathologic specimens show poor development of the adrenal zona glomerulosa and hyperplasia of the renal juxtaglomerular apparatus. Treatment with mineralocorticoid supplementation results in resumption of normal growth along with decreased excretion of DOC and corticosterone.

Genetics.

Molecular analyses of patients with CMO I deficiency show that CYP11B2 mutations obliterate all aldosterone synthase activity, rather than selectively impairing 18-hydroxylation.

18-Oxidase (CMO II) deficiency.

While both CMO Iand CMO II deficiencies are caused by CYP11B2 mutations, CMO II deficiency is more commonly encountered. Severe electrolyte abnormalities can occur in the neonatal period, with potentially life-threatening hyponatremia and hyperkalemia. Although electrolyte abnormalities and poor growth persist throughout early childhood, symptoms later in life are attenuated and eventually disappear. At the time of diagnosis, there are increased concentrations of corticosterone and 18-hydroxycorticosterone in plasma, with low aldosterone and high renin.

Adrenal hemorrhage of the newborn.

This occurs usually after a prolonged labor and traumatic delivery, often after toxemic pregnancy. It occurs more often in males than in females. Bleeding results from injury to the subcapsular vascular plexus of the adrenal glands, causing separation of the parenchyma from the capsule. Adrenal insufficiency results from the lack of vascular supply to the adrenal cortex. In order to cause symptomatic adrenal insufficiency, the hemorrhage must be bilateral.

The clinical picture is similar to that of an acute adrenal crisis, with hypoglycemia, hyponatremia, and hyperkalemia; newborns commonly also show hyperpyrexia, tachypnea, twitching, or convulsion. Enlarged adrenals may be palpable on physical examination or detected by sonography or radiography as a mass that displaces the kidneys downward. Bilateral adrenal hemorrhage can be confused with renal vein thrombosis, but in the latter condition there is normal adrenal function.

In infants who survive, adrenal calcification can be visible on x-ray for several months but tend to eventually resolve and disappear.

Adrenal hemorrhage associated with infection.

The normal adrenocortical response to acute infection is augmentation of cortisol production. However, patients with serious bacterial infections may develop acute adrenocortical insufficiency due to bilateral adrenal hemorrhage as a result of the effects of bacterial endotoxin. The most commonly associated bacterial pathogen is Neisseria meningitis. The adrenal crisis resulting from acute meningococcemia is also known as the “Waterhouse-Frederickson syndrome.” Other pathogens associated with septicemic adrenal hemorrhage include Pseudomonas aeruginosa, pneumococci, and streptococci.

Chronic hypoadrenocorticism (Addison disease).

Chronic primary adrenal insufficiency is referred to as Addison disease. It is rare in childhood and affects about 1 in 100,000 people in the general population. Autoimmune destruction of the adrenal cortex, as is seen in APSs, has replaced tuberculosis as the most frequent etiology (see Table 5-5). Up to 45% of patients with autoimmune Addison disease develop one or more other autoimmune endocrinopathies, most often thyroid disease (14%-25%). There is a slight preponderance of females, as is the case with autoimmune diseases in general. Type 1 APS is a rare autosomal recessive disorder resulting from mutations in the AutoImmune REgulator gene (AIRE), located on chromosome 21q22.3. Over 60 mutations of this gene have been reported. This gene is expressed in thyroid, lymph nodes, spleen, and fetal liver, and it regulates autoimmunity by promoting the ectopic expression of peripheral tissue-restricted antigens to medullary cells of the thymus. There is not a close association between genotype and phenotype in this heterogeneous disorder.⁵⁸ Among patients with AIRE mutations, 80% have Addison disease and 18% have type 1 diabetes.

In Addison disease associated with the more common condition of type 2 APS, as well as isolated autoimmune Addison disease, there is a specific HLA association. The highest risk of having both Addison disease and type 1 diabetes is associated with the heterozygous HLA DR4-DQ8/DR3-DQ2 genotype. Another genetic association with Addison disease is with a mutation in a nonclassic HLA molecule, MIC-A.⁵⁹

Pathogenesis in nonautoimmuneAddison disease

Nonbacterial pathogens may produce chronic adrenocortical insufficiency as a result of infiltration and destruction of the gland. In these cases, adrenal insufficiency progresses chronically, and adrenals may appear calcified on abdominal radiographs. The most common pathogen is tuberculosis, which was the etiology of adrenal insufficiency in Dr Addison’s first case description of the syndrome. Other rare causes are fungal infections such as histoplasmosis, coccidiomycosis, and blastomycosis.

Adrenocortical abnormalities have been described in association with HIV infection in patients with acquired immunodeficiency syndrome (AIDS) or AIDS-related complex. These abnormalities include either frank clinical symptoms of adrenal insufficiency, blunted cortisol response to acute ACTH stimulation, or decreased cortisol reserve after 3 days of ACTH stimulation despite elevated basal levels of cortisol. In children with HIV infection, basal and ACTH-stimulated cortisol levels are increased, suggesting an effect of chronic stress.

Adrenocortical insufficiency may result from a number of iatrogenic causes. Anticoagulant therapy may produce bilateral adrenal hemorrhage and acute adrenal insufficiency, even in the absence of bleeding elsewhere. A number of drugs may inhibit cortisol synthesis; however, if the inhibition is incomplete, it is usually compensated by increased ACTH secretion. These drugs include aminoglutethimide, ketoconazole, and etomidate. The drug o,p’-DDD, which is used in the treatment of Cushing syndrome, damages the mitochondria of the adrenocortical cells and may produce adrenal insufficiency.

Clinical features.

In primary adrenal failure, there is decreased or absent production of one or all three groups of adrenal steroid hormones. In most cases, the signs and symptoms of adrenal insufficiency develop slowly (see Table 5-4). Complaints of fatigue, muscle pain, weight loss, and orthostatic and gastrointestinal symptoms (nausea, vomiting, mild diarrhea) are frequent. In children, there may be growth failure. Patients may come to medical attention because of signs and symptoms of acute adrenal insufficiency precipitated by a febrile illness.

Hyperpigmentation is a hallmark of Addison disease, present in over 90% of patients, and may develop over a period of months to years. The typical distribution of hyperpigmentation is over the extensor surfaces of the extremities, particularly in sun-exposed areas. Mucous membranes (gingival borders, vaginal mucosa), axillae, and palmar creases are involved. The melanocytes are stimulated by excessively high levels of α-MSH, which is secreted concomitantly with ACTH from the anterior pituitary gland, as both are cleavage products of POMC.

Diagnosis.

The diagnosis is based on demonstration of elevated ACTH levels combined with decreased or absent cortisol and mineralocorticoid production. Fasting 8 am cortisol levels are low and fail to rise with ACTH stimulation. Fasting glucose may be low, and hyponatremia and hyperkalemia with acidosis may be present. Aldosterone levels are low, and PRA is usually elevated. Adrenal androgen levels may be below normal in adolescent and adult patients. Antiadrenal antibody (anti-21-hydroxylase antibody) level should be measured, as well as antibodies to other endocrine glands. In addition, serum calcium, phosphorus, and thyroxine levels should be measured because of the possibility of associated parathyroid and thyroid insufficiency. Of particular importance are the features that may cluster in either of the two types of APSs (see Table 5-5).

Hypoadrenocorticism Secondary to Deficient ACTH Secretion

Hypopituitarism

Deficient ACTH secretion can occur as a result of disorders characterized by a deficiency of one, some, or all of the peptide hormones secreted by the anterior pituitary gland, or as a result of deficient CRH secretion by the hypothalamus. Causes of reduced ACTH secretion are listed in Table 5-3.

Pathophysiology.

Congenital malformations of the brain, particularly midline defects, may result in hypothalamic insufficiency. Septo-optic dysplasia and its variants are such conditions. Congenital malformations of the pituitary can also occur, such as the hypoplastic pituitaries seen in some of the genetic defects in development of certain pituitary cell lineages (see Chapter 2). Trauma at delivery or later in life may result in infarction involving the hypothalamus and/or the pituitary. Infectious processes such as meningitis or encephalitis can result in hypopituitarism. Intracranial hemorrhage, as is seen in premature or very-low-birth- weight infants, may also produce hypopituitarism.

Infiltrative disorders that destroy normal tissues such as hemochromatosis, sarcoidosis, Langerhans histiocytosis, or granulomatous formations can also cause the loss of pituitary function. Treatment for various neoplasias including radiation therapy often impairs the secretion of pituitary tropic hormones. Finally, tumors arising inside the sella turcica (such as craniopharyngioma) or in the hypothalamus will often result in hypopituitarism. When no specific pathology is detected, the hypopituitarism is termed idiopathic.

Congenital defects in development of specific anterior pituitary cell lineages due to defective embryologically expressed transcription factors have been associated with ACTH deficiency. These include isolated ACTH deficiency due to TPIT mutations,⁶⁰ ACTH deficiency, associated with two or more additional pituitary hormone deficiencies, is also associated with mutations in GL12, OTX2, SOX3, HESX1 (septo-optic dysplasia locus), LHX4, LHX3, PROP1, and POU1F1.⁶¹

Clinical manifestations.

In congenital malformations of the brain or pituitary, the first symptom in the neonate of ACTH deficiency is usually hypoglycemia. When there is consistently low blood glucose, growth hormone, insulin, and cortisol concentrations should be measured at the time of the hypoglycemia. In pituitary disorders, cortisol and growth hormone are abnormally low and the insulin level is suppressed. In contrast, hyperinsulinism is characterized by inappropriately high or detectable insulin as well as high growth hormone and cortisol. MRI of the head may demonstrate underdevelopment of the optic chiasm and absence of the septum pellucidum, classic signs of septo-optic dysplasia (optic nerve hypoplasia). In male infants, a concomitant gonadotropin deficiency can be manifested by small genitalia and/or cryptorchidism. Other congenital malformations (such as cleft lip and/or palate) can also be associated with hypopituitarism.

It is difficult to relate hypopituitarism to a trauma of delivery or to a traumatic accident, unless there is clear-cut evidence of hemorrhage in the hypothalamic-pituitary area. Infections resulting in hypopituitarism often also impair mental development. Because of variation in the localization of brain tumors, patterns of tropic hormone insufficiency are variable and it may vary further after neurosurgery. Importantly, adrenal insufficiency due to ACTH deficiency does not lead to impairment of aldosterone secretion; therefore, these patients do not have a risk of salt wasting. Mild hyponatremia has been associated with cortisol deficiency. As many of these patients also have central hypothyroidism, the latter condition may contribute to the mild decrease in sodium concentration. Potassium levels are typically normal. However, antidiuretic hormone deficiency (diabetes insipidus), when it occurs, causes disturbance of electrolytes and water balance. Approximately one-half of the patients with idiopathic hypopituitarism have normal adrenocortical function, with the others usually having normal basal cortisol secretion with limited ability to increase their secretion during mild stress. However, they may respond to acute, marked stress such as IV high-dose ACTH test or IV insulin-induced hypoglycemia test.⁶² The IV ACTH stimulation test will identify those patients whose adrenal cortex is able to respond to ACTH. It does not assess the pituitary gland’s ability to secrete ACTH in response to stress. The insulin-induced hypoglycemia test assesses ACTH secretory ability, but many providers are hesitant to expose patients to hypoglycemia. The glucagon stimulation test also assesses ACTH secretory ability. In the case of a patient with documented low 0800 cortisol and ACTH levels who has a normal peak cortisol greater than 20 μg/dL with IV ACTH, one must consider that the pituitary may have recently lost its ability to secrete ACTH, but that the adrenal is still able to respond. Such patients may need cortisol replacement. A test of ACTH secretory capacity may be useful in this situation.

Patients with idiopathic isolated ACTH deficiency— with normal thyroid, growth hormone, and gonadotropin function—have been reported. Hypoglycemia during infancy is often the presenting symptom. Affected pubertal girls may have no or scant pubic hair because of lack of adrenal androgens. Mutations in the TPIT gene, which encodes a transcription factor required for fetal corticotroph development, is the cause of isolated congenital ACTH deficiency in some families.

Diagnosis.

ACTH deficiency causes low cortisol levels at any time of day, inadequate response of cortisol to stimulation tests such as the insulin-induced hypoglycemia or rapid IV ACTH tests, and low morning ACTH levels.

Cessation of glucocorticoid therapy

Glucocorticoid doses that exceed replacement requirements potentially suppress CRH and ACTH through the negative feedback mechanism that normally exists for the regulation of cortisol secretion. The general rules about hypoadrenocorticism due to withdrawal of steroid treatment are as follows:

1. If the dose of glucocorticoid administered was less than physiologic replacement therapy (ie, < ∼7 mg/m²/day HC equivalent), independent of the duration of the administration, there will be no major adrenocortical suppression.

2. If the dose of glucocorticoid administered was greater than replacement, there may be adrenocortical suppression:

   1. If the duration of therapy was less than 4 weeks, the suppression is likely to be transient with prompt recovery.

   2. If the duration of therapy was more than 4 weeks, the adrenocortical suppression can last from 1 week to 6 months. For these patients, it may be appropriate to resume glucocorticoid administration in the form of hydrocortisone in cases of stress for up to 6 months following cessation of treatment. If there is a need to document adrenocortical recovery, specific testing of the ACTH/cortisol axis may be necessary (Figure 5-17).

It must be noted that adrenocortical suppression can also occur after the cessation of topical steroid therapy such as inhaled corticosteroids, nasal spray, eye drops, or dermal creams and lotions.

Removal of a cortisol-secreting adrenal tumor

In cases of unilateral adrenocortical tumor producing cortisol and resulting in Cushing syndrome, the high concentration of circulating cortisol will suppress the endogenous CRH/ACTH secretion, resulting in atrophy of the contralateral adrenal. After removal of the tumor, the situation is similar to the cessation of glucocorticoid therapy. It is therefore appropriate to consider stress therapy with hydrocortisone for up to 6 months.

Infants born of steroid-treated mothers

Normally, only a fraction of maternal cortisol crosses the placenta to reach the fetus, such that maternal cortisol contributes about 10% of the fetal concentrations. However, with therapeutic doses well above the physiologic levels, significant placental passage of steroids could result in suppression of the fetal adrenal. Cortisol secretion of infants born of steroid-treated mothers is likely to be normal in cases involving prednisone usage, but more likely to be suppressed with dexamethasone administration, as this crosses the placenta quite freely. It is prudent to follow postnatal glucose concentrations of an infant born to a glucocorticoid-treated mother.

Hypoadrenocorticism Relatedto End-Organ Unresponsiveness

Unresponsiveness to aldosterone

Unresponsiveness of the kidney to aldosterone is a heterogeneous disorder known as pseudohypoaldosteronism (PHA). PHA type 1 (PHA1) presents in infancy with dehydration, hyponatremia, and hyperkalemia, despite marked elevations of plasma aldosterone and renin concentrations. Mineralocorticoid therapy is ineffective; patients respond only to sodium chloride supplementation.

PHA1 represents at least two disease entities of resistance to mineralocorticoid action. Autosomal dominant form is characterized by isolated renal unresponsiveness to aldosterone. Patients typically respond to oral salt supplementation, and severity of salt-wasting tendency improves with age. MR deficiency in PHA1 is caused by mutations in the type 2 steroid hormone (ie, mineralocorticoid) receptor gene.

In autosomal recessive PHA1, multiple organs contribute to salt loss, including kidney, colon, and salivary and sweat glands. The clinical course is more severe, and correction of life-threatening electrolyte abnormalities is difficult. In addition, patients may develop a chronic lung disease similar to cystic fibrosis. The molecular defect in AR PHA1 lies within subunits of the amiloride-sensitive epithelial sodium channel (ENaC).

In PHA type 2 (PHA2), there is hyperkalemia with metabolic acidosis, but, as opposed to PHA1, low renin hypertension is also present. These patients are effectively treated with diuretics. The molecular defect is within WNK 4 kinase.⁶³ WNK4 kinase regulates chloride cotransporters of the distal nephron as well as in other epithelial cells. These patients respond to sodium restriction and thiazide therapy.

Obstructive uropathy may cause renal resistance to aldosterone, which is usually reversible as the obstruction is treated and renal function returns to normal. The cause of aldosterone resistance is more common than the genetic causes described previously.

Cortisol resistance

Cortisol resistance is a rare autosomal dominant disorder typified by high plasma cortisol, ACTH, urinary free cortisol levels, and absent suppression of cortisol and ACTH by dexamethasone in an individual without clinical features of Cushing syndrome. A point mutation within the steroid-binding domain of the type 1 steroid hormone receptor or GR gene has been reported, inherited in autosomal dominant pattern. Cortisol resistance is usually partial and is compensated by elevated cortisol levels.

Naturally occurring variants of the human GR gene may confer increased or decreased sensitivity to cortisol. In addition, the GR itself has several different isoforms that mediate a wide variety of physiologic responses in a tissue-specific manner and may play a role in body fat stores and other biological responses.⁶⁴

ACTH resistance

• Familial glucocorticoid deficiency (FGD)— Genetic mutations of the ACTH receptor MC2R result in unresponsiveness to ACTH stimulation in the zona fasciculata, and reticularis reduces production of cortisol (FGD1). In contrast, the zona glomerulosa is unaffected and secretes aldosterone normally. FGD1 is an autosomal recessive disorder. Another form (FGD2) is due to a defect in a membrane protein that interacts with MC2R called MRAP.⁶⁵ Patients with FGD present early in childhood with feeding difficulties (eg, vomiting), failure to thrive, muscle weakness, hyperpigmentation, and hypoglycemia (which may result in seizures). Laboratory evaluation reveals low fasting serum glucose, normal electrolytes, subnormal but not undetectable plasma cortisol concentrations, and elevated plasma ACTH levels. Aldosterone secretion is normal and also increases appropriately with sodium restriction.

• Triple A syndrome—The combination of ACTH-resistant cortisol deficiency, achalasia, and absent lacrimation is known as the triple A syndrome (AAAS) or Allgrove syndrome. This autosomal recessive disorder results from a defect in the AAAS gene located on chromosome 12q13. Many patients have neurologic disorders, including peripheral, autonomic, and CNS impairments, and/or mild defects in mineralocorticoid (aldosterone) secretion, particularly when salt-restricted.⁶⁶

Approach to Clinical Management of Adrenal Insufficiency

Diagnosis of adrenal insufficiency

A proposed evaluation algorithm for patients with suspected adrenal insufficiency is shown in Figure 5-17. Different presenting signs will guide the evaluation. For example, findings of dehydration, hyponatremia, and hyperkalemia suggest primary adrenal failure with symptoms of both glucocorticoid and mineralocorticoid deficiencies. Hypoglycemia and/or a midline craniofacial defect suggest cortisol deficiency due to lack of ACTH effect.

Specific syndromes described previously may have additional diagnostic features, such as abnormal levels of cortisol precursors or other unique laboratory test results. Please see individual disease descriptions for details.

The normal ranges for blood and urinary glucocorticoids, and blood ACTH are shown in Table 5-6. Protocols and normal responses for stimulation tests are shown in Table 5-7.

Treatment of adrenal insufficiency

Medical treatment.

The goal of maintenance treatment is to administer a dose of cortisol equal to that normally secreted. The administered steroid produces a negative feedback on the hypothalamic-pituitary axis reducing CRH and ACTH secretion. This, in turn, suppresses the excessive secretion of cortisol precursors and adrenal androgens in CAH, and the excessive MSH secretion in Addison disease. In simple virilizing CAH, treatment replaces cortisol in amounts approximating the endogenous production, eliminates the mild salt-losing tendency, returns aldosterone secretion to normal, and suppresses androgen production and its virilizing effects.

Maintenance therapy.

Based on estimates of the ranges of normal cortisol secretion rate, a child requires a dose of 5 to 16 mg/m²/day of exogenous cortisol. An exact dose appropriate for individual patients may vary. Most favor the range of 6 to 8 mg/m²/day, but some patients may require doses in the higher range. Because of the short half-life of cortisol (hydrocortisone) given orally and its partial destruction by gastric acidity, optimal daily oral replacement dose may approximate 1.5 to 2 times normal daily cortisol secretion rate. The total daily oral dose of hydrocortisone should be divided into three fractions, given approximately every 8 hours. As the replacement dose is related to body surface area (as is the cortisol production rate), it is natural that the dose will need to be increased with growth.

Cortisol liquid for oral use (hydrocortisone) can be compounded as a suspension at a concentration of 2 mg/mL. The suspension must be shaken vigorously for several minutes to ensure homogeneity.⁶⁷ If this service is not available, 5-mg tablets can be crushed and suspended in a small amount of water (to ensure the full dose is taken).

Alternatively, prednisolone syrup (Prelone 1 or 3 mg/mL, Pediapred 1 mg/mL, or Orapred 3 mg/mL) can be used. These steroids are at least five times more potent than cortisol (daily dose 3-5 mg/m²/24 h) and have a longer half-life than cortisol, allowing twice daily dosing. Other synthetic glucocorticoid preparations, such as dexamethasone, have not often been used for replacement therapy in pediatrics, as their high potency makes it difficult to titrate dosage to avoid growth suppression or other adverse effects. However, protocols have been developed and tested using low-dose dexamethasone in CAH.^68,69 Prednisolone, prednisone, and dexamethasone lack significant mineralocorticoid activity (Table 5-8). In addition, for stress dosing the longer-acting more potent corticosteroids may be less preferable to oral or injected hydrocortisone, which produces more rapid plasma cortisol peaks.

While estimates of normal cortisol production rates help guide initial replacement, doses must then be adjusted to the clinical courses of individual patients. In addition, classic estimates of relative glucocorticoid potencies may have underestimated actual therapeutic potency, increasing the risk of overtreatment and cushingoid effects.

Therapy under stress conditions.

In patients with primary or central adrenal insufficiency, there is an inadequate cortisol response to stress. In milder forms of CAH, after approximately 4 weeks of exogenous cortisol therapy, the CRH-ACTH system is suppressed and unable to respond normally to stress. Thus, in both cases of cortisol replacement and iatrogenic suppression of ACTH, it is necessary to provide increased cortisol doses during situations of significant physiologic stress. Minor infection and/or low-grade fever (sore throat, runny nose, temperature up to 100.4°F) may not require a change in dosage. Conditions of moderate stress (severe upper respiratory infections, temperature > 100.4°F) warrant an increase in hydrocortisone dosage to approximately 25 to 30 mg/m²/day, divided tid. In situations involving major stress, with temperature above 102°F and/or vomiting, hydrocortisone dosing should increase to approximately 50 mg/m²/day, divided qid.

When infants and children are unable to retain oral medications (eg, repetitive vomiting within 30 minutes of dosing), administration of intramuscular cortisol sodium succinate (Solu-Cortef, dispensed in the form of a kit, Act-o-vial; Pfizer) is recommended. An age-based dose regimen (ie, < 3 years, 25 mg; 3-12 years, 50 mg; ≥ 12 years, 100 mg) will provide 4 to 6 hours of coverage, allowing time to seek medical treatment (Table 5-9). This emergency treatment is also recommended for loss of consciousness and seizures. Parenteral hydrocortisone can also be given as a rectal suppository (eg, commercially available 25-mg suppositories, or custom dosing compounded by a pharmacy), at a dose of approximately 100 mg/m². This route is often better accepted by families and patients than intramuscular injection.⁷⁰

An emergency letter outlining stress dosing should be provided to the family, which includes PO stress doses for moderate and severe illness, Solu-Cortef (Act-o-vial) IM dose, and contact information for the endocrinology center at a minimum. This letter should be given to the school, treating physician, and/or emergency responder by the family. Patients should wear or carry medical identification (eg, bracelet, necklace, shoe tag,) indicating that they have adrenal insufficiency and require hydrocortisone. Families and transitioning young adults should be taught how to administer the Solu-Cortef injection.

Therapy during surgical procedures.

During general anesthesia, with or without surgery, the cortisol secretion rate in normal subjects increases greatly. Similarly, in patients with adrenal insufficiency, the glucocorticoid requirement increases.

Although protocols vary, the following protocol from the 2002 consensus conference for CAH⁷⁰ is useful for surgical procedures that last longer than 30 to 45 minutes. The initial dose is given as an IV bolus followed by a continuous IV infusion. The stress doses of hydrocortisone are tapered rapidly according to the clinical improvement, generally by reducing the dose by 50% each day.

• 0-3 years: Hydrocortisone 25 mg IV, then 25-30 mg/day

• 3-12 years: Hydrocortisone 50 mg IV, then 50-60 mg/day

• ≥ 12 years: Hydrocortisone 100 mg IV, then 100 mg/day

For procedures lasting longer than 30 to 45 minutes, a rapid injection of 25 to 50 mg/m² of hydrocortisone sodium succinate (eg, Solu-Cortef) can be given IV just prior to anesthesia, followed by a dose of approximately 50 to 100 mg/m² as given as a constant infusion for the period of the surgical procedure.⁷⁰ If the patient is unable to take oral hydrocortisone postoperatively, a third dose of approximately 25 to 50 mg/m² hydrocortisone is given as a constant IV infusion for the rest of the first 24 hours of the surgical day. This is followed the next day by three to four times replacement therapy hydrocortisone given by constant IV infusion or orally. As hydrocortisone 40 mg has approximately the same mineralocorticoid effect as 0.2 mg of 9α-fluorocortisol, these high doses will provide both needed extra glucocorticoid and mineralocorticoid coverage. Stress dosing is generally continued until the patient can tolerate oral intake, is afebrile, and is hemodynamically stable. Box 5-2 lists the circumstances in which a patient with adrenal insufficiency should be referred to a pediatric endocrinologist.

Treatment of adrenal crisis

Rapid recognition and prompt electrolyte and fluid therapy of salt-wasting crises are critical to survival of these patients, especially infants. In patients without a specific diagnosis of adrenal insufficiency, appropriate blood samples must be obtained prior to treatment for measurement of cortisol, ACTH, steroid precursors (if suspicious for CAH), or VLCFAs if considering ALD and, in infants with ambiguous genitalia, a karyotype. Treatment of adrenal crisis is outlined in Table 5-9 and is initiated with a bolus of 20 mL/kg of 5% dextrose with normal saline given over 1 hour. Although this will correct plasma sodium and chloride concentrations, as well as hypoglycemia if present, the potassium concentration usually remains elevated and the acidosis may persist. Approximately 100 to 150 mL/kg of the same IV solution may be needed over the next 24 hours. Therapy with glucocorticoid and mineralocorticoid is started promptly. In newborn infants, an IV injection of25 mg of Solu-Cortef followed 20 to 25 mg of Solu-Cortef administered at a constant rate over the next 24-hour period is recommended. This 40- to 50-mg dose of cortisol is the equivalent of about 12 to 15 times replacement therapy for an infant with a normal body surface area of approximately 0.25 m², and has a salt-retaining activity of approximately 0.2 mg of 9α-fluorocortisol. If hyperkalemia is associated with electrocardiogram (ECG) changes, Kayexalate, or insulin and glucose treatment is advised. Throughout the treatment, electrolytes and water balance must be monitored very carefully in order to avoid hypernatremia, water retention, and possible pulmonary edema.

Mineralocorticoid-replacement therapy.

The only mineralocorticoid preparation currently available is 9α-fluorocortisol given orally at a dose of 0.05 to0.2 mg/24 h. During an adrenal crisis, the routine fludrocortisone dose should be continued if the patient can tolerate enteral therapy. In infancy, breast milk or prepared formula provides very little salt (8-10 mEq of sodium per 24 hours), and mineralocorticoid replacement alone may not be sufficient to sustain salt and water balance. For this reason, 20 to 40 mEq of sodium chloride is usually added to the regimen, divided into three or four daily doses. This can be prescribed as a 2- or 4-mEq/mL solution or prepared by the parents by mixing salt into the infant formula or breast milk. One-fourth of a teaspoon of table salt is about 20 mEq of sodium. When the diet of the child becomes more varied and includes solid food, which is usually rich in sodium, the salt supplement is no longer required.

CAH—special considerations

The criteria for determining appropriate cortisol dosing in CAH due to CYP21A2 deficiency include the concentration of 17-hydroxyprogesterone and androstenedione in plasma, and the close follow-up of somatic growth (weight, bone age, and height and weight velocities). In affected children, levels of plasma androstenedione should be in the prepubertal reference range. However, regarding 17-hydroxyprogesterone, normal prepubertal concentrations (0 to 80 ng/day) usually indicate overtreatment, levels of approximately 500 ng/dL are acceptable, and concentrations of more than 1000 ng/dL usually indicate insufficient therapy. The 17-hydroxyprogesterone level may be affected by the timing of the measurement in relation to the last medication dose and time of day. In order to reduce this variation, blood samples can be obtained at the same time of day with each laboratory draw. Serum concentrations of androstenedione show less variability with dosing and time of day. In older children entering puberty, the normal range for androstenedione increases as it is also secreted by the gonads. In general, females with androstenedione levels at the lower end of the reference range or even below have a more normal onset and progression of ovarian maturation and its feminizing effects. In boys the progression of puberty is not as impacted by slightly higher androstenedione levels.

Regarding monitoring for adequate mineralocorticoid replacement, electrolytes are useful and are usually normal except in the setting of illness or noncompliance. PRA in the normal range is desired. A suppressed PRAmay indicate that the fludrocortisone dose can be reduced, but only if the patient has not been consuming excess fluid and/or salt prior to the laboratory test. Blood pressure should be carefully followed, and one should consider reducing the fludrocortisone dose in the setting of hypertension that is documented by several readings.

Patients should be evaluated regularly during the growing years, with more frequent follow-up during periods of rapid growth such as infancy and puberty. Infants should be flowed every 1 to 2 months while they are younger than 1 year, every 3 months until 2 to 3 years. If stable, they can be followed every 6 months. When puberty begins, especially in females, it may be necessary to return to monitoring every 3 months.

Patients with simple virilizing CAH have normal serum electrolytes and do not have an absolute requirement for mineralocorticoid replacement therapy. However, in the clinical setting of difficulty in suppressing adequately the adrenal androgen excess, combined with an elevated PRA, mineralocorticoid treatment may improve suppression and avoid deleterious effects of higher cortisol replacement doses. Proposed mechanisms for this beneficial effect include suppression of vasopressin secretion and its stimulation of ACTH production by increased intravascular volume and enhancement of cortisol effect by the minor glucocorticoid effect of fludrocortisone.

During the growth period of the child, glucocorticoid dosage generally requires increase in relation to increasing body size, although there is considerable variation in individual requirements. Further, apart from body size, there appears to be a temporal variation of requirement (Figure 5-18). In infancy, the average required dose is much higher than it is in childhood, followed by another increase at the time of puberty.

Surgical reconstruction of the external genitalia of female CAH patients.

Girls with the salt-wasting form of CAH, in general, have more completely masculinized external genitalia, and it is recommended that females with a Prader stage 3 or greater, clitoral and perineal reconstruction be considered in infancy, with neurovascular-sparing clitoroplasty and vaginoplasty using a total or partial urogenital mobilization technique.²²

Adjunct and alternative therapies.

⁷¹ Some female patients with CAH (including nonclassic) may have enough ovarian secretion of androgen to require addition of ovarian suppressive therapy (oral contraceptives) to reduce the virilizing symptoms. In some females with salt-wasting CAH, results of therapy are suboptimal, with androgen excess remaining problematic and refractory to suppression with physiologic cortisol replacement dosages. Bilateral adrenalectomy has been proposed as a possible means of improving these results; however, this treatment remains controversial and should only be considered in cases that have failed medical therapy; in particular, cases of adult females with salt-wasting CAH who are infertile.²² Other approaches to treatment have included peripheral blockade of androgen action and estrogen production with flutamide (antiandrogen) and testolactone (aromatase inhibitor), in combination with reduced hydrocortisone, and fludrocortisone. It is important to emphasize that such alternatives are presently experimental and many years of follow-up will be required to judge their validity.⁷⁰

Psychological treatment.

In all patients with CAH, there is a risk of psychological problems related to having a chronic disease. In females this is complicated by a history of ambiguous genitalia and genital surgery. Adjustment is usually improved when the patient and parents understand the pathogenesis of the disorder. Appropriate glucocorticoid treatment will remediate the chronic androgen excess, and thus adherence to treatment recommendations should prevent androgen excess at puberty. There is some evidence that prenatal androgen exposure influences postnatal behavior in some females with CAH, such as male-typical play preferences, but this is highly variable.⁷² Girls with CAH (5-12 years old) have been found to have absent gender-identity confusion/dysphoria⁷³ or a slight increase in atypical gender identity compared to control girls.⁷⁴ In adult women with CAH, serious gender identity issues were present in a small minority of patients raised female.⁷⁵ A psychological gender evaluation may be warranted in certain 46,XX patients with CAH, ideally as part of a multidisciplinary team that includes a mental health clinician with expertise in DSD.²² It has been postulated that childhood play behavior could be associated with sexual orientation,⁷⁶ with bi- and homosexual orientation in a minority of patients.

Treatment of ACTH deficiency.

Patients with multiple pituitary hormone deficiencies require replacement of the deficient cortisol along with other deficient hormones. When basal cortisol secretion is abnormally low, both maintenance and stress therapy are required. When basal concentrations are normal but the rapid IV ACTH test or glucagon test is abnormal, only stress therapy may be required.

In patients with a deficiency of both TSH and ACTH, cortisol replacement should be initiated prior to thyroxine replacement, as thyroid replacement in absence of glucocorticoid may result in symptoms of acute adrenal insufficiency. GH also has effects on cortisol metabolism, decreasing cortisone to cortisol through reduction in hepatic 11β-HSD1 activity and increasing CYP3A4-mediated glucocorticoid catabolism. Thus, initiation of hGH replacement can theoretically unmask underlying ACTH deficiency or reduce the effect of current cortisol replacement and stress dosing. On occasion, ADH deficiency is unmasked shortly after starting cortisol replacement therapy. As cortisol is needed to excrete a water load, cortisol deficiency partially corrects the diuresis of diabetes insipidus.

Hyperadrenocorticism

Classification of adrenocortical overactivity syndromes is usually based on the clinical findings related to the specific hormone that is in excess. In some cases, there are several hormones that are oversecreted together.

Cushing syndrome, a state of cortisol excess, had a number of different etiologies (Table 5-10), including Cushing disease resulting from hypersecretion of ACTH, and other causes of cortisol excess such as primary adrenal sources and iatrogenic causes. The so-called adrenogenital syndrome results from hypersecretion of adrenal androgens from either CAH (see earlier) or masculinizing adrenal tumors. Masculinizing tumors secrete androgen, and in many cases also secrete cortisol. Feminizingadrenal tumors cause excess estrogen secretion of adrenal origin. These tumors rarely secrete only estrogen, and in most cases secrete both estrogen and androgen. They are termed “feminizing tumors” if the estrogen effects predominate. Primary hyperaldosteronism or Conn syndrome is due to excessive secretion of aldosterone. Similar clinical findings may also result from dexamethasone-suppressible hypertension or apparent mineralocorticoid excess (AME).

Cushing syndrome

If one excludes iatrogenic causes, Cushing syndrome is rare in infancy and childhood. In all age groups, there is a two- to threefold predominance of females. The signs and symptoms may develop over a short period of time, and after cure will regress rapidly (Figure 5-19).

Clinical manifestations.

Cushing syndrome is characterized by hypercortisolism, and its clinical features represent an exaggeration of the physiologic effects of cortisol (Table 5-11, see Table 5-1). Effects on skeletal muscle and fat are manifested as wasting of the extremities, truncal obesity, moon facies, and cervical fat pad (“buffalo hump”). Skeletal effects in all age groups included osteoporosis and osteomalacia. In children, there is marked inhibition of skeletal growth and maturation, resulting in short stature and delayed bone age. This contrasts markedly with the growth acceleration and advanced bone age associated with common nutritional obesity in childhood. Effects on collagen result in atrophy and thinning of the skin, and violaceous striae characteristically on the abdomen and hips. Capillary fragility is another effect, and it is manifested by easy bruisability. Hypertension is an inconsistent finding and may result from the salt-retaining effect of cortisol or other substances. Muscle weakness and fatigue can reflect hypokalemia, if present. CNS effects of excess cortisol are not well understood, but they may include broad mood swings, psychosis, and idiopathic intracranial hypertension. Stimulation of gastric acid secretion by excess cortisol may cause dyspepsia and gastric ulcers. The latter is more common in adults than in children.

In some patients, cortisol excess is accompanied by oversecretion of adrenal androgens, and typical cushingoid features are accompanied by generalized virilism or hirsutism (excess hair growth of the face, extremities, trunk, and pubic area). In some children, marked androgen effects may occur, and the time course of these changes is generally more rapid than that seen in virilizing CAH or precocious puberty.

Laboratory diagnosis

General.

Hematological parameters show an increase in neutrophils and perhaps a high hematocrit. Electrolytes may reveal hypokalemia and/or hypochloremia. There is expansion of intravascular fluid volume, despite the stimulatory effect of cortisol on free water excretion at physiologic concentrations. Calcium concentration in the blood is usually normal despite its increased urinary excretion. Serum phosphate may be low.

Plasma amino acid concentrations are elevated because of protein catabolism. Plasma insulin levels are elevated as a result of the cortisol-related insulin resistance. Hyperglycemia and glucosuria may develop due to insulin resistance and gluconeogenesis. Hyperlipidemia may result from increased lipolysis stimulated by cortisol excess, as well as the increased insulin-stimulated conversion of glucose to lipids.

Cortisol and ACTH concentrations.

Demonstration of excess cortisol required to diagnose Cushing syndrome often requires complex and tedious testing. Random measurement of cortisol concentration is a helpful screening test; however, increase in ACTH and cortisol during stressful situations, particularly phlebotomy in children, can yield falsely positive results. Because patients with Cushing syndrome have both elevation of cortisol and loss of normal diurnal variation, levels should be obtained at both 8 am and 4 pm or later for analysis. A serum cortisol level at midnight more than 7.5 μg/dL has very high specificity and sensitivity for Cushing syndrome and a level of less than 1.8 μg/dL at that time essentially excludes the diagnosis.

ACTH should be measured simultaneously with cortisol. Low or undetectable ACTH concentration (< 10 pg/dL) in the midst of high cortisol suggests adrenal tumor. If the level of ACTH in the late afternoon is not suppressed (> 20 pg/dL) in the face of high cortisol, stress or ACTH-dependent Cushing must be considered. In some patients with suspected ACTH-dependent Cushing disease, ACTH levels measured on samples obtained from the inferior petrosal sinus can aid the localization of the ACTH secreting lesion.

Midnight salivary cortisol is another useful diagnostic test for Cushing syndrome. The sample can be collected at home, away from the stress of the health care facility or phlebotomy. In adults, cutoff values vary, but values more than 0.55 μg/dL suggest Cushing syndrome and those less than 0.35 μg/dL rule against it.^15,77

Urinary steroid excretion.

The excretion of free cortisol is a useful assessment of the 24-hour secretion of cortisol. Urinary free cortisol is a direct reflection of unbound, biologically active cortisol in blood. Urinary excretion of free cortisol is expressed as μg/day, corrected for surface area, or (particularly for children) corrected for creatinine excretion as μg/mg creatinine/day. Values over 70 μg/m²/day or over 25 mg/g creatinine (see Table 5-6) are considered elevated and deserving of further evaluation.

Dexamethasone suppression tests.

Suppression ofACTH secretion with dexamethasone is useful in determining the etiology of ACTH-dependent Cushing syndrome. Suppression is usually attempted with a low-dose or overnight test. An oral dose of 1.25 mg/m²(or 1.0 mg in adults) is administered at midnight, and cortisol concentration is measured at 8 am to 9 am the following morning. A normal response is defined as a cortisol of less than or equal to 1.8 μg/dL. Failure of suppression leads to the next step, with a higher dose of dexamethasone. Protocols vary but include the Liddle 2-day test (0.5 mg every 6 hours for eight doses, starting at 9 am). After 48 hours, cortisol is measured. A single-dose high-dose test using 8 mg dexamethasone followed by tests for cortisol the following morning can also be used. In general, ACTH-dependent Cushing due to a pituitary tumor will show suppression with the high-dose but not the low-dose test. Ectopic ACTH secreting tumors and CRH-secreting tumors are less likely to suppress with high-dose dexamethasone. As an alternative to measuring the cortisol response to dexamethasone, the 24-hour urinary free cortisol can be followed. Whereas these avoid the stress of phlebotomy, they are not commonly used because of their cumbersome and error-prone collections.

CRH stimulation test.

The IV administration of ovine CRH, 100 μg/m² (100 μg in adults), causes an exaggerated ACTH response at 30 minutes and cortisol response at 60 minutes in patients with pituitary Cushing disease. Patients with ectopic secretion of ACTH or adrenal tumors do not show this pattern. Some investigators have demonstrated the usefulness in combining the CRH test before and after the 48-hour dexamethasone suppression test. This combination has been shown to differentiate between Cushing syndrome and pseudo-Cushing syndrome; in the latter case the ACTH response is blunted relative to Cushing syndrome.

Key clinical recommendations

• Differentiating the hypercortisolism of Cushing syndrome from that of obesity—Patients with obesity have elevated cortisol secretion rates and urinary excretion of cortisol. Correction of these values for body surface area normalizes them in many subjects, but not in all. In response to the low-dose dexamethasone suppression test, obese subjects typically show normal suppression of serum cortisol concentration at 8 am.

  Determining the etiology of hypercortisolism— In patients with clinical evidence of Cushing syndrome who have elevated blood, salivary, and urinary cortisol concentrations, it is necessary to determine the etiology in order to recommend treatment. Exogenous sources such as oral, topical, or inhaled steroids must be ruled out. In addition, possible pseudo-Cushing syndrome, most often secondary to chronic alcoholism or depression, should be considered based on clinical history, laboratory findings (Table 5-12). Pseudo-Cushing syndrome is cured when the underlying cause is effectively treated.

  An approach to the diagnosis of Cushingsyndrome in pediatric patients is shown inFigure 5-20. In general, initial screening tests include measurement of plasma cortisol and ACTH at 8 am and 4 pm, and midnight blood or salivary cortisol. If elevated, urinary excretion of free cortisol corrected for creatinine are determined. If these results are elevated, the next step is a low-dose or overnight dexamethasone suppression test. If suppression is adequate, Cushing syndrome is unlikely. If not, further testing with CRH stimulation, high-dose dexamethasone suppression, or both are indicated.

• Radiologic studies for the determination of the etiology of hypercortisolism—Radiologic imaging studies are necessary to localize the source of excess hormone secretion. CT scans are the study of choice to detect adrenal hyperplasia caused by ACTH hypersecretion and bilateral micronodular adrenal hyperplasia, and unilateral adrenal tumors accompanied by contralateral adrenal atrophy. CT scanning can also detect ectopic ACTH secreting tumors, most often located in the lungs. The latter tumors are quite rare in childhood.

  MRI is the study of choice for brain imaging. Unfortunately, despite their marked clinical effects, many ACTH-secreting pituitary basophilic adenomas are small and undetectable. Because surgical resection represents a cure, tumor localization by bilateral inferior petrosal sinus sampling for ACTH levels can be extremely important prior to surgical resection. The sensitivity of this study is enhanced by measuring ACTH before, and 15 and 30 minutes after administration of IV CRH.

Treatment

ACTH-dependent Cushing disease

• Pituitary adenoma—The treatment of choice is resection of the pituitary tumor, which, if complete, is curative. This is most often accomplished through the transsphenoidal route. If not successful, pituitary radiation is a generally effective second-line treatment. The most common side effect of the radiation is growth hormone deficiency, which occurs in more than 80% of patients. Most patients will have transient suppression of the normal ACTH axis after surgery, necessitating corticosteroid replacement therapy for several months. Ectopic ACTH-secreting tumor—Localization and resection of the source are the main goals of treatment. As most of these tumors are highly malignant, treatment generally involves a combination of surgery, radiation, and chemotherapy.

• Adrenocortical tumors—In young children, 80% of Cushing syndrome is caused by a unilateral adrenal tumor. Adrenal tumors can also arise from ectopic adrenal tissue, such as in the liver. Unfortunately, these are often malignant carcinomas demonstrating local invasion or distant metastases at the time of diagnosis. If detected early, surgical resection can be curative. Distant metastases generally involve the lung, bone, and liver. An unusually high prevalence of these tumors in southern Brazil has been associated with TP53 R337H germline mutations.⁷⁸

  Complete surgical resection of an adrenal carcinoma in a patient without metastases is generally curative. After surgical resection, patients with more advanced carcinomas may or may not benefit from radiation to the tumor bed. Chemotherapeutic regimens for patients with metastatic disease are generally effective but may not be curative. Adrenal adenomas have an excellent prognosis for complete cure after surgical resection.

  After surgical resection of an adrenal tumor, there is a high risk of suppression of the CRH/ACTH/adrenal axis. The atrophied contralateral adrenal usually recovers within 6 months; thus corticosteroid therapy must be provided postoperatively, and the dosage very slowly reduced to avoid adrenal insufficiency.

• Bilateral adrenal hyperplasia—The most common cause of this condition is ACTH-dependent Cushing syndrome, and treatment is the removal of the source of excess ACTH or CRH. Other more unusual causes are described as follows.

• Food-dependent Cushing syndrome—In these patients, bilateral macronodular adrenal hyperplasia is because of an aberrant receptor causing adrenal responsiveness to gastric inhibitory polypeptide (GIP). These patients, who have intermittent Cushing syndrome and cortisol elevations, have low ACTH levels, normal fasting cortisol concentration, and increases in plasma cortisol in response to ingestion of food or infusion of GIP. This effect can be effectively blocked with octreotide.

• Bilateral micronodular adrenal hyperplasia— This rare condition is due to constitutively activated ACTH receptors on the adrenocortical cells. This activation results from mutations of the gene encoding the α-subunit of the stimulatory G protein, Gsα. These patients, who usually also have other manifestations of this mutation as seen in the McCune-Albright syndrome, require bilateral adrenalectomy to cure the hypercortisolism. Isolated Cushing Syndrome may be the presenting sign of McCune-Albright syndrome.⁷⁹

• Medical treatment of Cushing syndrome. Medications may offer palliation in patients with Cushing syndrome that cannot be curedsurgically. These include steroidogenic inhibitors (mitotane, metyrapone, aminoglutethimide, and ketoconazole) and inhibitors of ACTH secretion (bromocriptine, cyproheptadine, valproic acid, and octreotide). GR antagonism with RU-486 (mifepristone) and a somatostatin receptor antagonist, pasireotide, have been used with some success in adult patients.^80,81

Virilizing Tumors

Virilizing tumors are the most common adrenocortical tumors of childhood. In most parts of the world they remain rare, but certain clusters suggest environmental factors or genetic contributions in isolated populations. These tumors tend to have a twofold female preponderance and are unusual in the first year of life.

Clinical manifestations.

In females, the tumors cause hirsutism and virilization. Usually, pubic hair appears first, followed by clitoromegaly. In older girls, the hyperandrogenism prevents normal pubertal maturation; thus breast development is delayed. In prepubertal males, there is also marked hirsutism. There is pubic hair development and growth of the phallus, without testicular enlargement. In both sexes, there is increased muscle mass, rapid skeletal growth, advanced bone age, and occasional hemihypertrophy. The tumors are rarely large enough to be detected by abdominal palpation.

Hormone levels.

Virilizing tumors secrete large amounts of androgen precursors without ACTH stimulation. Most patients have marked elevation of urinary 17-ketosteroids. A large fraction of the blood androgens are conjugated as sulfates, with a predominance of DHEA-S and androsterone. Among the unconjugated androgens, there is a marked increase in DHEA, testosterone, and androstenedione. The elevated testosterone appears to be of adrenal origin, as opposed to the peripheral conversion of androstenedione to testosterone seen in CAH. Most patients have normal cortisol secretion, and normal electrolytes and aldosterone secretion.

Pathology.

Patients with virilizing tumors that also secret excess cortisol have a poorer prognosis, and differentiating an adenoma from a carcinoma is often difficult. Carcinomas tend to be larger and more vascular, with heterogeneous areas of cystic formation, hemorrhage, and necrosis. In advanced carcinomas, there is local invasion of the kidney or liver.

Diagnosis

• Androgen secretion—Urinary 17-ketosteroid excretion and plasma androgen levels are elevated, especially concentrations of DHEA and DHEA-S. In most cases, over 50% of the fractionated 17-KS will be DHEA.

• Dexamethasone suppression test—In contrast to hyperandrogenism from CAH, androgen secretion from adrenal tumors is not suppressible. If dexamethasone 1.25 mg/m²/day orally, divided every 8 hours for 5 to 7 days, causes little or no change in urinary 17-ketosteroid excretion or blood androgen levels, an adrenocortical tumor is suspected.

• Imaging studies—Abdominal CT is the preferred method of detecting adrenal tumors, although MRI may be used as well.

Differential diagnosis.

The differential diagnosis of virilization includes androgens from adrenal, gonadal, or exogenous origins. In girls, possibilities include ovarian tumors, premature adrenarche, precocious puberty, PCOS, or CAH. In boys, possibilities include premature adrenarche, gonadotropin-dependent or -independent precocious puberty, Leydig cell tumor of the testis, or ectopic hCG secretion from tumors such as a hepatoma or dysgerminoma. Exposure to exogenous androgens must be ruled out in both sexes.

Treatment.

The primary treatment is localization and surgical resection of the tumor. In most cases, if the tumor does not also produce Cushing syndrome, the lesion is fairly small and can be completely resected, resulting in a cure. In the rare metastatic tumors, both primary and metastatic tumors are resected as completely as possible. When metastases are widespread and cannot be surgically resected, radiotherapy and chemotherapy are usually offered.

After surgery, careful monitoring for recurrence includes serial measurements of adrenal androgens and examination for clinical signs of androgen excess.

Feminizing tumors

These tumors are rare in childhood and usually produce increased androgens as well as estrogens.⁸²

Clinical manifestations.

In prepubertal children of both sexes, the tumor is usually small and nonpalpable at the time of diagnosis. There is rapid growth with skeletal age advancement.

Boys usually present with gynecomastia. The genitalia appear normal in size, and pubic and axillary hair are usually absent if there is no androgen hypersecretion. In prepubertal girls, there is premature breast development with estrogenization of the vaginal mucosa. There may be episodes of vaginal spotting. In the absence of hyperandrogenism, there is no development of pubic or axillary hair. In pubertal girls, the diagnosis is more difficult and is often made later in the development of the tumor.

Diagnostic studies.

Blood concentrations of estrogens are generally elevated for age but may be in the range seen in adult women. Blood DHEA-S and other androgenic steroids may be elevated as a result of concomitant secretion of adrenal androgens (especially DHEA) and may resemble that seen in virilizing tumors. As with virilizing tumors, some patients with feminizing tumors may also manifest increased cortisol secretion and features of Cushing syndrome.

• Dexamethasone suppression—Estrogen secretion is not decreased by dexamethasone suppression, as the secretion is not ACTH-dependent.

• Imaging studies—CT of the abdomen is the study of choice.

Pathology.

The general appearance and histology of feminizing tumors is similar to that of virilizing tumors. In many patients, it may be difficult to determine that the tumor is benign, but long-term survival of many patients following surgery suggests a low degree of malignancy.

Differential diagnosis.

In patients of both sexes, an exogenous source of estrogen (eg, oral contraceptives or Premarin) must be ruled out. Certain cosmetic and hair care products may also contain estrogens, such as those derived from placental extracts, lavender oil, and tea tree oil.⁸³

In boys, other causes of gynecomastia include benign pubertal gynecomastia (accompanied by testicular enlargement, a feature generally not present in patients with feminizing tumors), drugs (eg, reserpine, digoxin, and marijuana), Klinefelter syndrome, and partial androgen insensitivity. Feminizing testicular tumors are rare but are in the differential diagnosis.

In prepubertal girls, premature thelarche and precocious puberty should be excluded. Elevated estrogen caused by an ovarian cyst or tumor could be diagnosed based on ultrasound examination of the ovaries. In pubertal or postpubertal girls, the diagnosis is often delayed.

Treatment.

Prompt resection of feminizing tumors is the preferred treatment and is usually curative. As these tumors generally do not produce excess cortisol, adrenal suppression is unlikely. If the bone age has been significantly advanced prior to resection of the tumor, central precocious puberty may occur postoperatively.

Hyperaldosteronism

Syndromes of mineralocorticoid excess are rare in childhood (Table 5-13) and can be subdivided into those with elevated aldosterone levels (true aldosterone excess) and those with features of aldosterone excess but no elevation of aldosterone levels (AME). These features include hypokalemia and hypertension.

True aldosterone excess.

In conditions of aldosterone excess, plasma levels of aldosterone are elevated, and hypokalemia is present. Patients may or may not have elevated renin levels or hypertension, depending on the etiology.

Primary hyperaldosteronism results from autonomous adrenocortical hypersecretion of aldosterone due to bilateral nodular hyperplasia of the adrenal cortex (idiopathic hyperaldosteronism [IHA]) or an adrenocortical tumor (adenoma or carcinoma). Patients present with hypertension, hypokalemia, elevated plasma aldosterone levels, and low PRA. In IHA, adrenal glands exhibit focal hyperplasia of normal zona glomerulosa cells, accompanied by adrenocortical nodules. Patients with IHA are treated medically with spironolactone, a competitive inhibitor of the MR, which is usually quite effective in managing the hypertension.

Hyperaldosteronism caused by an adrenocortical tumor may present with the same signs and symptoms as IHA. However, a unilateral source of aldosterone hypersecretion may be demonstrated by selective adrenal vein sampling for aldosterone levels, and a mass may be visible by radiologic imaging studies (CT or MRI scan). Adenomas are more common than carcinomas, and they may also produce cortisol in a normal diurnal pattern. In adults, primary aldosteronism more often results from an adenoma than IHA. The treatment of choice is surgical resection of the tumor.

Dexamethasone-suppressible hyperaldosteronism or glucocorticoid-remediable aldosteronism (GRA) is a rare autosomal dominant form of low renin aldosterone excess with hypertension, hypokalemia, low PRA, elevated aldosterone levels, and lack of the normal aldosterone escape with continuous infusion of synthetic ACTH. The unique features of this syndrome are the rapid reduction of aldosterone levels into the normal range by administration of dexamethasone, and the failure of aldosterone infusion to produce hypertension in the dexamethasone-suppressed patient.

The pathogenesis of GRA is a persistent and unregulated overproduction of mineralocorticoids, eventually leading to hypertension and hypokalemia. The recognition that two distinct gene products perform the terminal steps in biosynthesis of mineralocorticoid (CYP11B2) and glucocorticoid (CYP11B1) led to the discovery that a hybrid CYP11B1/CYP11B2 gene caused the disorder (see Figure 5-15).⁸⁴ The promoter-regulatory sequences derived from CYP11B1 direct ACTH-responsive expression of the chimeric gene in the inner (fasciculata and reticularis) cortical zones. The chimeric protein, by virtue of critical amino acids encoded by CYP11B2, performs all reactions required for aldosterone production, thus causing ACTH-dependent hyperaldosteronism. Ectopic expression of the chimeric protein in the inner cortical zones, which also expresses CYP17A1, permits the formation of 18-hydroxy and 18-oxocortisol, the biochemical hallmarks of GRA.

Treatment with glucocorticoids, by suppressing the steroidogenesis of the zona fasciculata and reticularis, alleviates the hypertension.³⁰ Determining the optimal dose of glucocorticoid can be difficult in children in whom glucocorticoid requirements vary markedly at different stages of development. Alternative therapies include mineralocorticoid antagonists such as spironolactone, which competitively inhibits the MR, and amiloride, which indirectly inhibits mineralocorticoid actions in the kidney.

In hyperreninemic hyperaldosteronism, the aldosterone hypersecretion is secondary to excessive renin production by the renal juxtaglomerular cells. The most common etiology of this condition is renal ischemia. In such patients, the hypertension may be responsive to medical therapy with ACE inhibitors. Therapy directed toward correction of the underlying cause of the renal ischemia should be undertaken when possible.

Apparent mineralocorticoid excess.

This is an autosomal recessive disorder caused by deficiency of the enzyme 11β-HSD2, which is necessary for the conversion of cortisol to its inactive metabolite cortisone. In 11β-HSD2 deficiency, inappropriately high intrarenal levels of cortisol result in a clinical picture consistent with mineralocorticoid excess through its binding to the steroid type 2 or MR. Under physiologic conditions the MR, which has equal affinities for glucocorticoids and mineralocorticoids, is exposed essentially only to mineralocorticoids because of the efficient activity of 11β-HSD2 in the kidney. In patients with congenital AME, interaction of cortisol with the MR produces volume expansion, sodium retention, hypertension, and hypokalemia. Plasma levels of renin and aldosterone are below normal. Patients with this disease have severe hypertension that is resistant to medical management. The human gene encoding 11β-HSD2 has been cloned and mapped to chromosome 1. The molecular genetic defects in patients with AME include small intragenic deletions, missense mutations, and one intronic defect altering normal splicing. Most patients are homozygotes, suggesting a founder effect. Treatment consists of low-salt diet, potassium supplementation, and spironolactone.

AME may be acquired by licorice intoxication. Patients who ingest excessive amounts of licorice may develop hypertension, hypokalemia, and fluid retention with low plasma levels of aldosterone and renin. The active components on licorice are glycyrrhizic acid and its metabolite glycyrrhetinic acid, both of which inhibit 11β-HSD type 2 activity. The signs and symptoms of mineralocorticoid excess resolve within several weeks after discontinuation of licorice; however, complete reversal of the renin-angiotensin system suppression may take several months.⁸⁴

Disorders of the Adrenal Medulla

Normal hormone physiology

The adrenal medulla consists of chromaffin tissue, innervated by sympathetic nerves that originate in the splanchnic system. This sympathoadrenal system is controlled by a complex set of central neural connections that are involved in the production, storage, and secretion of catecholamines. In addition, the adrenal medulla is exposed to relatively high concentrations of glucocorticoids in the venous drainage of the adrenal cortex, which is required for a normal epinephrine response to stress. In patients with glucocorticoid deficiency due to ACTH unresponsiveness, there is a marked loss of basal epinephrine secretion, as well as in the epinephrine response to upright posture, cold pressor, and exercise. These individuals have a slight compensatory increase in norepinephrine. In patients with CAH caused by CYP21A2 deficiency, ACTH suppression with maintenance glucocorticoid treatment reduces the adrenal medullary hormone output.

The major catecholamines in humans are dopamine, norepinephrine, and epinephrine, all of which are synthesized primarily in nerve endings. Dopamine is produced mainly in the brain, norepinephrine mainly in the sympathetic nerve endings (and to a limited extent in the adrenal medulla), and epinephrine in the adrenal medulla where it is the major product. The o’-methylated metabolites of catecholamines are excreted in the urine as fractionated metanephrines. They can also be measured as free metanephrines in the plasma.

The biosynthesis of catecholamines is illustrated in Figure 5-21. Tyrosine is hydroxylated to form DOPA, which is then converted to dopamine, a neurotransmitter within the CNS. Dopamine also acts as the precursor for synthesis of norepinephrine, the principal neurotransmitter of the sympathetic nervous system. Norepinephrine is then converted to epinephrine in an enzymatic step that is controlled by glucocorticoid. Epinephrine exerts its physiologic effects by interaction with both alpha (α₁ and α₂) and beta (β₁ and β₂) adrenergic receptors. The physiologic effects of epinephrine are widespread and are separated into the differing alpha and beta effects (Table 5-14, see Chapter 1).

Tests of adrenal medullary function

Measurement of single random catecholamine concentrations in the blood, that is, norepinephrine and epinephrine, is rarely helpful, as patients who have excess production may have periods of low blood concentrations, and patients with normal production will have appropriately high concentrations in response to stress. Moreover, in normal children and adolescents, plasma epinephrine and metanephrine decrease with advancing pubertal stage, and are generally higher in boys than in girls. These hormone levels correlate inversely with blood concentrations of DHEA-S, estradiol, testosterone, leptin, and insulin.

Patients who have symptoms suggesting possible catecholamine excess are better evaluated under controlled conditions by measurement of catecholamines and their metabolites normetanephrine, metanephrine, homovanillic acid (HVA), and vanillylmandelic acid (VMA) in a 24-hour urine sample. This gives an assessment of integrated catecholamine production. The metabolic pathways in the degradation of catecholamines are illustrated in Figure 5-21. Serial measurements of these compounds in blood and urine after paroxysmal attacks of catecholamine release may also be informative. Measurement of plasma catecholamine concentrations, if obtained in the fasting supine individual after 30 minutes of rest, can be as reliable as urinary metanephrine concentrations in predicting the presence of pheochromocytoma, but the false-negative rate is fairly high.

There has been a recent trend toward the use of fractionated urinary metanephrines and plasma-free metanephrines in the evaluation of patients with suspected pheochromocytoma. The combination of 24-hour urinary catecholamines and fractionated metanephrines may yield less false positives than the plasma-free metanephrines, but the latter may be of more value in high-risk patients.⁸⁵

Some medications (radiocontrast dyes, acetaminophen, antihypertensives, monoamine oxidase inhibitors, methyldopa, quinidine, tetracyclines, and bronchodilators) may alter the results of blood or urinary catecholamine measurements. Urinary VMA concentrations may be falsely elevated by certain drugs such as aspirin, penicillin, and sulfa preparations. In addition, some dietary components (certain fruits, chocolate, vanilla, caffeine) may also affect these assays.

Several provocative tests are available to aid in the diagnosis of the etiology of elevated catecholamine concentrations, should plasma and urinary catecholamine concentrations not be diagnostic. Because these tests can entail significant risks in some patients, including hypertensive crisis, provocative tests should only be performed in patients who have a patent IV catheter, and with phentolamine (an α-adrenergic blocking agent) available for immediate IV infusion, if needed.

The glucagon stimulation test produces a rise in blood catecholamine concentrations and often a rise in blood pressure, but it has less risk than histamine or tyramine stimulation tests. Glucagon (1.0-2.0 mg in adults) is given as an IV bolus, and plasma catecholamines and blood pressure are measured 1 to 3 minutes later. The test is considered positive for pheochromocytoma if there is a threefold increase in catecholamine concentrations, or an increase to a concentration greater than 2000 pg/mL.

The histamine stimulation test (0.025-0.05 mg IV) causes a normal drop in blood pressure followed by a secondary rise. The plasma and urinary catecholamine concentrations rise after histamine in patients with pheochromocytoma.

Clonidine, a centrally acting α-adrenergic agonist, decreases plasma catecholamine concentrations (sum of epinephrine and norepinephrine concentrations) to less than 500 pg/mL in normal subjects and in patients with essential hypertension. Patients with pheochromocytoma do not show a drop in plasma catecholamine concentrations to this degree. Hypotension is a potentially serious side effect of this test, especially in patients receiving β-adrenergic blocking agents.

Radiologic studies are invaluable in the diagnosis of adrenal medullary tumors and other causes of catecholamine excess. A CT or MRI scan may identify masses of the adrenal medulla or sympathetic chain. Selective catheterization for adrenal venous sampling may allow lateralization of a source of excess catecholamine production. Nuclear medicine studies allowing localization of catecholamine-producing tumors have become possible through the use of the isotope ¹³¹I-metaiodobenzylguanidine (MIBG). MIBG is similar in structure to norepinephrine and is an analog of guanethidine. It is concentrated in tissues that are actively synthesizing catecholamines by means of uptake into norepinephrine storage granules.

Clinical entities

Most abnormalities of the adrenal medulla are attributed to tumors, either benign or malignant, which secrete catecholamines.

Pheochromocytoma is rare in childhood but must always be considered in a child with hypertension or other symptoms of catecholamine excess. This tumor may arise from any chromaffin tissue, but it is most often found in the adrenal medulla. Extra-adrenal catecholamine-secreting tumors are referred to as paragangliomas. Bilateral adrenal or extra-adrenal tumors are more common in children than in adults and are often associated with familial pheochromocytoma or the multiple endocrine neoplasia (MEN) syndromes, as well as the von Hippel-Lindau syndrome. Pheochromocytomas are also associated with neuroectodermal dysplasias (eg, neurofibromatosis). Approximately 40% of childhood pheochromocytomas have a hereditary cause, including MEN syndromes (Table 5-15), paraganglioma syndromes, von Hippel-Lindau, and neurofibromatosis.⁸⁶ The neoplasms associated with these syndromes are listed in Table 5-15. Features consistent with these associated tumors, for example, medullary carcinoma of the thyroid, should be sought in any patient with pheochromocytoma. The MEN syndromes are inherited in an autosomal dominant manner and have variable expression. Pheochromocytoma is benign in greater than 90% of pediatric cases. There is a male preponderance during childhood; however, the sex ratio is reversed in adults.

Diagnosis.

Signs and symptoms of pheochromocytoma are those of catecholamine excess, and include hypertension, sweating, palpitations, headache, nausea, polyuria with polydipsia, and emotional lability. These features are highly variable among different patients and are likely to be paroxysmal in nature. However, hypertension may be sustained, and a hypertensive crisis may occur during anesthesia necessitating adequate medical preparation for surgical procedures. Diagnosis of pheochromocytoma is based on demonstration of increased concentrations of catecholamines and their metabolites in blood (catecholamine concentrations> 2000 pg/mL) and/or a 24-hour urine sample (exceeding 200-300 μg/24 h). The predominant urinary catecholamine in children with pheochromocytoma is norepinephrine, whereas in adults both epinephrine and norepinephrine excretions are usually elevated. The use of fractionated urinary metanephrine excretion is also helpful. If the results are inconclusive, a pharmacologic stimulation or suppression test may be indicated. If suspected by biochemical tests, the tumor can usually be localized by radiologic imaging. Venography to demonstrate elevated concentrations of catecholamines should only be performed after adequate α-blockade to prevent a hypertensive crisis.

The molecular bases of the syndromes associated with childhood pheochromocytoma are now known. The defective gene in the MEN1 syndrome is called the MEN1 gene, which is a tumor-suppressor gene located on chromosome 11q13. Mutations of this gene do not have a strong genotype-phenotype relation in this syndrome, and the penetrance of pheochromocytomas in this syndrome is low. Somatic mutations of this gene also occur in sporadic adrenocortical tumors. MEN2 is caused by mutations in the RET proto-oncogene on chromosome 10. This gene is also defective in familial medullary thyroid carcinoma. The penetrance of pheochromocytoma in MEN2 is fairly high. The von Hippel-Lindau tumor suppressor gene on chromosome 3p25 is defective in that syndrome, andin familial pheochromocytoma. Defective genes in the familial paraganglioma syndrome are SDHD (chromosome 11q23) and SDHB (chromosome 1p36) that encode subunits of the mitochondrial complex II SDH enzyme complex. Neurofibromatosis type 1 is caused by defects in the NF1 gene on chromosome 17q11.2. Additional genetic associations with pheochromocytoma and paraganglioma include TMEM127, MYC-associated factor X, and hypoxia-inducible factor (HIF) 2α.⁸⁶

Treatment.

Treatment of pheochromocytoma is surgical excision following preparation with α-adrenergic blockade, using either oral phenoxybenzamine (nonselective α-antagonist), prazosin (specific α₁-blocker), or doxazosin for 7 to 10 days to reduce vasoconstriction and restore depleted intravascular volume. Patients with arrhythmias should also receive presurgical treatment with β-adrenergic blocking agents after adequate α-blockade is achieved. Medical management may also include metyrosine, which decreases catecholamine biosynthesis up to 80% by inhibiting tyrosine hydroxylase activity. This enzyme is the initial and rate-limiting step in the conversion of tyrosine to dihydroxyphenylalanine (DOPA) (see Figure 5-21).

Intraoperative management of hypertensive crises uses IV phentolamine or sodium nitroprusside. If bilateral adrenalectomy is necessary, glucocorticoid and mineralocorticoid treatment for primary adrenal insufficiency must be promptly instituted. Postoperative follow-up of blood pressure and catecholamine concentrations is needed to monitor for tumor recurrence.

Malignant tumors are diagnosed on the basis of functional tumor in nonchromaffin tissue areas. Benign tumors may cause blood vessel or capsular invasion but do not spread beyond chromaffin tissue areas. Malignant tumors grow slowly, are resistant to radiation and chemotherapy, and the symptoms may be treated medically with α-methyl tyrosine (an inhibitor of catecholamine synthesis) with variable success.

Neuroblastoma, a malignant tumor of neural crest origin, is a common solid tumor of childhood. Neuroblastomas may arise from the adrenal medulla as well as from other sympathetic nervous tissue. As these tumors secrete catecholamines, the diagnosis can often be made by demonstration of elevated HVA and/or VMA concentrations in the urine. In general, urinary concentrations of epinephrine, norepinephrine, metanephrines, and VMA are lower in neuroblastoma than in pheochromocytoma, whereas concentrations of dopamine and HVA tend to be higher. Hypertension is less common in neuroblastoma than in pheochromocytoma. These tumors may also secrete neuropeptides such as vasoactive intestinal peptide (VIP), gastrin-releasing peptide (GRP), substance P, pancreastatin, and neuropeptide Y (NPY). Pediatric reference ranges for these peptides have been developed, potentially aiding in the interpretation of their levels in patients with suspected neuroblastoma. Radiologic localization is usually achieved with CT or MRI scanning.

Genetic studies of neuroblastomas reveal that many tumors contain karyotypic abnormalities. There is frequently a deletion of distal chromosome 1p (1p32-1pter), which has been found in other tumor lines as well. Presence of the 1p deletion within a neuroblastoma correlates with decreased patient survival. Many neuroblastoma cells also contain areas of chromatin that are composed of amplified genes, occurring either as extrachromosomal double minute chromosomes or as intrachromosomal homologously staining regions. The amplified gene in these regions is the N-myc proto-oncogene, so termed because of its similarity to c-myc. N-myc is normally expressed in a variety of fetal tissues, but not normally in differentiated cells. Neuroblastoma cells contain somatostatin receptors, particularly of the subtype 2. This may eventually allow targeting of this receptor for diagnostic and therapeutic purposes with radiolabeled somatostatin analogs.

Other tumors of adrenal medullary origin include ganglioneuroblastoma and ganglioneuroma. These tumors, as well as neuroblastoma and pheochromocytoma, may present with chronic watery diarrhea caused by tumor secretion of VIP. Catecholamine-releasing nonadrenal tumors may mimic pheochromocytoma. These include paraganglioma (mentioned above) and astrocytoma.