91: Disorders of Sex Development

Ambiguous genitalia are present when the sex of an infant is not readily apparent after examination of the external genitalia. If the appearance resembles neither a male with a normal phallus and palpable testes nor a female with an unfused vaginal orifice and absence of an enlarged phallic structure, the genitalia are ambiguous, and investigation before gender assignment is indicated. The recent trend has been to refer to these disorders as disorders of sex development (DSDs) because many of the other terms used are considered pejorative by some patients and professionals. Also, the term “atypical genitalia” instead of “ambiguous genitalia” has been suggested. New definitions and classifications are also being proposed in this already very complex area. For the purpose of this on-call manual, the embryology and pathophysiology are reviewed as relevant to the initial evaluation and treatment of patients in the neonatal period.

The quoted incidence of ambiguous genitalia varies according to the source and is likely somewhat variable for different ethnic groups; it appears to be ∼1 in 5000. Congenital adrenal hyperplasia is often considered the most common cause with an incidence quoted from 1 in 14,000 to 1 in 28,000, followed by androgen insensitivity and mixed gonadal dysgenesis. Hypospadias has a frequency of about 1 in 300 births, but only a minority of these patients has a disorder of sex development (usually presenting with hypospadias in combination with cryptorchidism).

The early fetus, regardless of the genetic sex (XX or XY), is bipotential and can undergo either male or female differentiation. The innate tendency of the embryo is to differentiate along female lines.

1. Development of the gonads. Gonadal development occurs during the embryonic period (the third through the seventh to eighth weeks of gestation).

   1. Testicular differentiation. Gonadal differentiation is determined by the absence or presence of the Y chromosome. If the Y chromosome (more specifically, the sex-determining region of the Y or SRY gene) is present, the gonads differentiate as testes. The testes then produce and release testosterone, which is converted to dihydrotestosterone (DHT) in the target organ cells by 5α-reductase. DHT induces male differentiation of the external genitalia (see Section III.B.1). The testes descend behind the peritoneum and normally reach the scrotum by the eighth or ninth month.

   2. Ovarian differentiation. In the female fetus, where the Y chromosome/SRY gene is absent, the gonads form ovaries (even in 45,X Turner syndrome, histologically normal ovaries are present at birth). As ovaries do not produce testosterone, female differentiation proceeds. Two X chromosomes are needed for differentiation of the primordial follicle. If part or all of the second X chromosome is missing, ovarian development fails, resulting in atrophic, whitish, streaky gonads by 1–2 years of age.

2. Development of external genitalia. This part of sexual differentiation occurs in the fetal period, beginning in the seventh week of gestation, and proceeds up to the 14th week (about 16 weeks after the last menstrual period).

   1. Normal male. At ∼9 weeks postconceptional age, in the presence of systemic androgens (especially DHT), masculinization begins with lengthening of the anogenital distance. The urogenital and labioscrotal folds fuse in the midline (beginning caudally and progressing anteriorly), leading to the formation of the scrotum and the penis.

   2. Normal female. In the female fetus, the anogenital distance does not increase. The urogenital and labioscrotal folds do not fuse and instead differentiate into the labia majora and minora. The urogenital sinus divides into the urethra and the vagina.

1. Virilization of female infants (female pseudohermaphroditism). Many neonates with disorders of sex development belong to this group. They have a 46,XX karyotype, are SRY negative, and have exclusively ovarian tissue. The degree of masculinization of the female newborn depends on the potency of the androgenic stimulation to which she is exposed, the stage of development at the time of initial exposure, and the duration of exposure.

   1. The most common cause of excess fetal androgens is an autosomal recessively inherited enzymatic deficiency in the cortisol pathway, leading to excessive corticotropin (adrenocorticotropic hormone [ACTH]) stimulation with congenital adrenal hyperplasia (CAH) and excessive production of adrenal androgens (dehydroepiandrosterone and androstenedione) and testosterone (Figure 91–1). Most common is 21-hydroxylase deficiency, which causes inadequate cortisol levels, leading to excessive ACTH stimulation (through feedback to the hypothalamus and pituitary), adrenal hyperplasia, and excessive production of adrenal androgens (dehydroepiandrosterone and androstenedione) and testosterone, producing virilization. Two forms of CAH are seen in neonates, depending on the associated relative or absolute aldosterone deficiency: a simple virilizing form and a salt-losing form. In the first form, the salt loss is mild and adrenal insufficiency tends not to occur, except in stressful circumstances. In the second, adrenal insufficiency occurs under basal conditions and tends to manifest in the neonatal period or soon thereafter as an adrenal crisis. The electrolyte status of all infants with 21-hydroxylase deficiency should be monitored because the extent of virilization is not a reliable indicator of the degree of adrenal insufficiency. 11-Hydroxylase enzyme deficiency is less common and associated with salt retention, volume expansion, and hypertension.

   2. Other, less common causes. Virilizing maternal or fetal tumors or maternal androgen ingestion or topical use.

2. Inadequate virilization of male infants (male pseudohermaphroditism). This condition is caused by inadequate androgen production or incomplete end-organ response to androgen. These patients have a 46,XY karyotype and exclusively testicular tissue. These abnormalities are rare, and most require extensive laboratory investigation before a final diagnosis can be confirmed.

   1. Decreased androgen production. This can be caused by one of several rare enzyme defects, which are inherited in an autosomal recessive manner. Some of these defects also cause cortisol deficiency and nonvirilizing adrenal hyperplasia, and others are specific to the testosterone pathway. Other causes of decreased androgen production include deficiency of Müllerian-inhibiting substance (the most common presentation is a male infant with inguinal hernias that contain a uterus or fallopian tubes); testicular unresponsiveness to human chorionic gonadotropin (hCG) and luteinizing hormone (LH); and anorchia (absent testes caused by loss of vascular supply to the testis during fetal life). The association of microphallus/micropenis and hypoglycemia suggests a pituitary deficiency with absence of gonadotropins, ACTH, or growth hormone.

   2. Decreased end-organ response to androgen. Also referred to as testicular feminization, can be caused by a defect in the androgen receptor or an unknown defect with normal receptors. It can be total (labial testes with otherwise normal-appearing female genitalia) or, more commonly, partial (incomplete virilization of a male).

   3. 5α-Reductase deficiency. Results in failure of the external genitalia to undergo male differentiation because of the lack of DHT (see Figure 91–1). The outcome is a neonate with female or atypical genitalia but with a 46,XY karyotype, normally developed testes, and male internal ducts.

3. Disorders of gonadal differentiation

   1. True hermaphroditism. The presence of both a testis and an ovary (or ovotestes) in the same individual is a rare cause of ambiguous genitalia. Most individuals with true hermaphroditism have a 46,XX karyotype, but mosaics of 46,XX/45,X/46,XY/multiple X/multiple Y have all been reported. The appearance of the genitalia is variable; fertility is poor.

   2. Gonadal dysgenesis

      1. Pure gonadal dysgenesis. Characterized by the presence of a streak gonad bilaterally (complete gonadal dysgenesis) or unilaterally (partial gonadal dysgenesis). It is important to distinguish the X-chromosomal from the Y-chromosomal form because the streak gonads in the Y-positive patients carry a significant risk for tumor development.

      2. Mixed gonadal dysgenesis. Characterized by the presence of a unilateral functioning testis and a contralateral streak gonad. All patients have a Y chromosome and some degree of virilization of the external genitalia. Mixed gonadal dysgenesis is associated with a high incidence of gonadal malignancy in mid to late childhood.

4. Chromosome abnormalities, syndromes, and associations. In general, chromosomal abnormalities do not usually lead to genital abnormalities. However, disruption of normal sex development has been reported occasionally in trisomies 13 and 18, triploidy, and a number of other chromosomal anomalies. Single-gene disorders and syndromes such as Smith-Lemli-Opitz syndrome, Rieger syndrome, CHARGE syndrome (coloboma, heart defects, choanal atresia, retarded growth and development, genital abnormalities, and ear anomalies), camptomelic dysplasia, and others can also be associated with external sexual ambiguity (>90 syndromes with “ambiguous genitalia” were found in a search of a syndrome database). VATER/VACTERL (vertebral, anal, tracheal, esophageal, renal dysplasia/vertebral defects, anal atresia, cardiac malformations, tracheoesophageal fistula, renal dysplasia, and limb abnormalities) association can include abnormally developed genitalia.

The etiology of disorders of sex development is developmental/genetic. Therefore, there are no definite behavioral risk factors, but a history of relatives with genital anomalies, abnormal pubertal development, infertility, or neonatal/infant deaths could be an indicator of increased risk. The question of whether techniques of assisted reproduction, especially in vitro fertilization with intracytoplasmic sperm injection, may be associated with disorders of sex development and other birth defects remains controversial because the abnormalities reported could also be related to the underlying cause of infertility leading to the use of these techniques rather than an association with the process of assisted reproduction.

Note that the American Academy of Pediatrics issued a policy statement on the evaluation of the newborn with developmental anomalies of the external genitalia in 2000. In 2006, after an International Conference on Intersex, a “Consensus Statement on the Management of Intersex Disorders” was published (see Selected References).

1. History. A careful history should be obtained from the parents. Family history of early neonatal deaths (a death in early infancy accompanied by vomiting and dehydration may be secondary to CAH), consanguinity of the parents (increased risk for autosomal recessive disorders), and female relatives with amenorrhea and infertility (male pseudohermaphroditism or chromosomal anomalies) are significant, as are a maternal history of virilization or CAH and ingestion or topical use of drugs during pregnancy (particularly androgens or progestational agents).

2. Physical examination

   1. General examination. A general examination should address the presence of any of the following: dysmorphic features (syndromes and chromosomal abnormalities), hypertension or hypotension, areolar hyperpigmentation, and signs of dehydration (as signs of CAH).

   2. Genitalia. Gonads: The number, size, and symmetry of gonads should be evaluated. Palpable gonads below the inguinal canal are usually testes. Ovaries are not found in scrotal folds or in the inguinal region. However, the testes may be intra-abdominal. Phallus length: Measured from the pubic ramus to the tip of the glands, a stretched penile length in a full-term infant should be ≥2.0 cm. Reference values for premature infants have been established; ethnic background may influence penile length. Urethral meatus: Look for hypospadias (usually accompanied by chordee). Labioscrotal folds: Findings can range from unfused labia majora, variable degrees of posterior fusion, and bifid scrotum to fully fused, normal-appearing scrotum. The presence of a vaginal opening or urogenital sinus should be determined. A rectal examination, to determine presence of a uterus, may be considered.

1. Laboratory studies

   1. Initial evaluation. An important test in the initial evaluation is the chromosome analysis. Most cytogenetic laboratories can now provide preliminary results of a karyotype in a few days. Fluorescent in situ hybridization techniques (FISH) allow even faster determination of the sex chromosome status; X- and Y-specific probes are available. Buccal smears are unreliable and therefore obsolete. The remainder of the diagnostic evaluation depends on the sex chromosome status. Blood for basic biochemical studies can be obtained at the same time as the karyotype, including 17-hydroxyprogesterone (17-OHP), testosterone, dihydrotestosterone, sodium, and potassium levels. Other tests may be necessary, depending on the results of the karyotype. Biochemical tests are therefore discussed in the context of the different chromosomal constellations.

   2. Normal 46, XX karyotype. This finding implies virilization of a genetic female and is caused by excessive maternal or fetal androgen. If the mother is not virilized, the infant almost always has virilizing adrenal hyperplasia. To confirm the diagnosis, measure the following:

      1. 17-hydroxyprogesterone (17-OHP). This is the immediate precursor to the enzyme defect in 21-hydroxylase enzyme deficiency and a precursor one step further removed in 11-hydroxylase enzyme deficiency. In infants with either defect, the serum or plasma level of 17-OHP will be 100–1000 times the normal infant level. Note that the 17-OHP level may be somewhat elevated in normal infants within the first 24 hours of life; a repeat level several days later may be indicated while fluid and electrolyte balance is monitored. 17-OHP is now measured by many newborn screening programs in the United States and other countries as a screening for CAH.

      2. Daily serum measurements of sodium and potassium. Infants with 21-hydroxylase enzyme deficiency usually have relative or absolute aldosterone deficiency and begin to demonstrate hyperkalemia at days 3–5 and hyponatremia 1–2 days later. If hyperkalemia becomes clinically significant before the 17-OHP result is available, empirical treatment with intravenous saline, cortisol, and fludrocortisone may be needed (for dosages, see Section VIII.B.1a and b).

      3. Serum testosterone. About 3% of infants with ambiguous genitalia are true hermaphrodites, and most have a 46,XX karyotype. If the 17-OHP is not elevated and there is no maternal virilization, a high testosterone level suggests hermaphroditism or fetal testosterone-producing tumor.

   3. Normal 46,XY karyotype. The differential diagnosis of an incompletely virilized genetic male is extremely complex and includes in utero testicular damage, defects of testosterone synthesis, end-organ resistance, and an enzymatic defect in the conversion of testosterone to dihydrotestosterone. The laboratory evaluation is correspondingly complex and usually proceeds through a number of steps.

      1. Testosterone (T) and dihydrotestosterone (DHT). These hormone levels should be measurable and are higher in newborns than later in childhood. In the male pseudohermaphrodite, testosterone is low in any defect in testosterone production. The T-to-DHT ratio should be between 5:1 and 20:1 when expressed in similar units. A high T-to-DHT ratio suggests 5α-reductase deficiency (see also Section VII.A.3c). Androstenedione levels are measured to diagnose 17-ketosteroid reductase deficiency.

      2. LH and follicle-stimulating hormone (FSH). These hormones are also higher in infancy than they are in childhood. A diagnosis of gonadotropin deficiency is suspected if these values are low in a reliable assay but can be confirmed in infancy only if there are other pituitary hormone deficits (see Section VII.A.3d). Note that growth hormone and ACTH deficiency are manifested in the newborn period as hypoglycemia. In primary gonadal defects and some androgen-resistant states, LH and FSH are elevated.

      3. hCG stimulation test. hCG is administered to stimulate gonadal steroid production when testosterone values are low (as in gonadotropin deficiency or a defect in testosterone synthesis). Recommendations vary, and the test should be performed under the guidance of a specialist. In general, a dose of 500–1000 U every day or every other day for 3 doses may be given. Then testosterone and DHT are measured again to evaluate the gonadal response. A rise in the testosterone level confirms the presence of Leydig cells and, by implication, testicular tissue. In patients with 5α-reductase deficiency, the basal T-to-DHT ratio may be normal but elevated after hCG stimulation. It is wise to obtain enough blood after hCG injection to measure other steroid intermediates if the testosterone is low. Considering the complexity of male pseudohermaphroditism, the restrictions in drawing blood from newborns, and the fact that many specific tests can be performed only in special laboratories, involvement of a pediatric endocrinologist in the planning and interpretation of these tests is crucial. In any case, it is always advisable to ask the initial processing laboratory to freeze any remaining serum or plasma.

      4. Assessment of pituitary function. If gonadotropin deficiency due to impairment of pituitary function is suspected (eg, microphallus/micropenis combined with hypoglycemia), thyroid function tests, growth hormone levels, ACTH stimulation test, and imaging studies of the pituitary gland may be indicated.

   4. Abnormal karyotype. Mixed gonadal dysgenesis with a dysplastic gonad may be present in infants with abnormal karyotype and abnormal genitalia. Hormone studies are unlikely to be revealing in this scenario. Note that a normal karyotype from peripheral white blood cells does not exclude mosaic chromosomal abnormalities, and there is a limit in the resolution of conventional karyotypes. Special genetic testing (FISH analysis, genome microarray analysis, or specific DNA analysis) may be needed. These techniques may allow detection of SRY gene material in 46,XX phenotypic males and be useful in determining whether Y material is present in a 45,X individual, placing the patient at risk for gonadoblastoma.

2. Radiographic studies

   1. Ultrasonography to evaluate adrenal and pelvic structures. Although a uterus is sometimes palpable on rectal examination shortly after birth (because of enlargement in response to maternal estrogen), ultrasonography seems less invasive. The presence and localization of gonads may also be clarified by ultrasonography. Adrenal ultrasonography is sufficiently sensitive to determine adrenal abnormalities in the majority of patients with untreated adrenal hyperplasia.

   2. Contrast studies to outline the internal anatomy (sinography, urethrography, vesicocystoureterography, and intravenous urography) may be indicated in complex cases and before reconstructive surgery.

   3. Magnetic resonance imaging (MRI) has been used to evaluate patients with disorders of sex development but, at least in the neonatal period, sensitivity may only be marginally improved over ultrasound.

1. General considerations. The presence of any disorders of sex differentiation is likely to cause significant emotional and social stresses and anxieties for the family. It is very important to protect the privacy of child and parents while diagnostic studies are in progress. A multidisciplinary team should assist the patient and family throughout the diagnostic process and beyond. Once a diagnosis has been established, gender should be assigned (see Section IX) and a team of specialists should supervise medical treatment (steroid replacement, gonadal removal, reconstructive surgery, etc.) and treatment of psychosocial aspects. Circumcision should be delayed in any infant with a DSD until completion of multidisciplinary evaluation and gender assignment.

   1. Early interactions with the parents and general care. As soon as the abnormality is noted, a physician responsible for the infant should be identified and the parents should be informed. During the initial counseling of the family, gender neutral terms such as “your infant” should be used; gender-specific pronouns should be avoided. A phrase often recommended in this situation is to refer to the genitalia as “incompletely developed.” Parents should be informed that it is not possible without further tests to identify the sex of their child. Meet with the parents as soon as possible to discuss the situation in more detail (the delivery room is usually not appropriate for an in-depth discussion). The feelings, impressions, and biases perceived at the time parents first learn about the diagnosis of a sex differentiation disorder often persist. Examining the infant with the parents may be beneficial, but any attempts to identify the sex of the child on the basis of appearance should be resisted, although there is likely to be great pressure to do so from parents, relatives, and hospital personnel. It is important not to complete the birth certificate or make any reference to gender in any of the permanent medical records of the mother or the child. It may be advisable to isolate the child and parents from the inquiries of certain nonessential hospital personnel and the community, but any actions implying that the condition is shameful or should be “hidden” must be avoided. Parents may want to delay sending out birth announcements and telling anyone outside the immediate family that the infant has been born until a gender assignment has been made. Be aware that many children live the majority of their lives in the community of their birth, and confusion about gender assignment because of premature release of information may have long-term consequences. Parents should be reassured that in most cases the gender will be determined as soon as test results are available, and some specialists discourage the use of unisex/epicene names in the early neonatal period.

   2. Early referral. It is advisable to seek consultation from a specialist in the evaluation of children with disorders of sex differentiation (the first specialist involved is often a pediatric endocrinologist) as soon as feasible. It is usually not appropriate to discharge a child from the nursery before a detailed evaluation is done. In most cases, a complete diagnosis, assignment of the sex of rearing, and a plan for future treatment can be accomplished before discharge.

2. Medical management in the neonatal period and early infancy

   1. Congenital adrenal hyperplasia. The most immediate concern in a neonate with abnormal genitalia is whether CAH is present. The onset of adrenal insufficiency occurs between days 3 and 14 in 50% of affected patients. All forms of adrenal hyperplasia have absolute or relative cortisol deficiency and require early diagnosis and replacement therapy to prevent potential life-threatening complications such as vascular collapse.

      1. Glucocorticoid therapy. Should be initiated as soon as possible. Maintenance cortisol replacement therapy is often given orally. Hydrocortisone is the oral preparation of choice. (See Chapter 148.) Initial doses usually range from 10 to 20 mg/m²/d given as 3 divided doses and often require adjustments for growth and during periods of stress. Alternatively, intramuscular cortisone acetate is sometimes used in children <6 months of age out of concern that oral hydrocortisone may be absorbed erratically in these infants. Supervision of replacement therapy and long-term follow-up with a pediatric endocrinologist is advised; institutional practices may vary.

      2. Mineralocorticoid therapy. Fludrocortisone acetate at a dose of 0.05–0.1 mg daily (given orally) is often used. Unlike hydrocortisone, the dose of fludrocortisone does not change with increase of body size or during stress. Some endocrinologists also recommend sodium supplementation (1–5 mEq/kg/d).

   2. Incompletely virilized genetic male. Treatment with depo-testosterone might be considered by the team of specialists depending on the results of the diagnostic evaluation.

Discussion surrounding issues of gender assignment are beyond the scope of this book. In general, the sex of rearing should be determined only after diagnostic evaluation by a specialist team. In the past, gender assignment had been approached as though individuals are psychosexually neutral at birth and as though healthy psychosexual development is related to the appearance of the external genitals. However, these beliefs have been challenged. It is now believed that prenatal and early exposure of the brain to androgens, if present, influences gender-specific behavioral patterns and sexual identity in addition to the external appearance of the genitalia or their future function. Considering the significance of the decision for the affected patient's emotional, physical, and reproductive health, a highly specialized multidisciplinary team of pediatricians, urologists, endocrinologists, geneticists, psychiatrists, and others is needed, and each case must be approached individually. Specialized treatment centers should provide long-term care to optimize prognosis. The Consortium on Disorders of Sex Development maintains a website with clinical guidelines and information for families (www.dsdguidelines.org), as do many other support groups such as the Intersex Society of North America (www.isna.org), the Congenital Adrenal Hyperplasia Support and Education (CARES) Foundation (www.caresfoundation.org), and others.