- Adrenal insufficiency (AI) results from deficiency of glucocorticoid (cortisol) and mineralocorticoid (aldosterone) secreted by the adrenal cortex.
- Glucocorticoid deficiency impairs gluconeogenesis and glycogenolysis, resulting in fasting hypoglycemia.
- Aldosterone deficiency results in decreased sodium retention by the kidney and distal renal tubular exchange of potassium and hydrogen ions for sodium, resulting in osmotic diuresis, hyponatremia, hypovolemia, hyperkalemia, acidosis, and prerenal azotemia.
- AI is classified into primary (adrenocortical failure itself), secondary (pituitary), or tertiary (hypothalamic) types. AI, because of withdrawal from exogenous steroid administration, is the most common cause of adrenal crisis.
- Symptoms of AI are usually nonspecific such as fatigue, anorexia, abdominal pain, nausea, or diarrhea but it can present as cardiovascular collapse or shock and hence a high index of suspicion is required.
- The most common cause of primary AI in infants is congenital adrenal hyperplasia (CAH).
- Acquired causes of primary AI in children are less common than congenital disorders.
- Acquired AI results from autoimmune, infectious, infiltrative, hemorrhagic, or toxic causes.
- Acute management consists of rapid fluid resuscitation, correction of hypoglycemia, hyperkalemia, and acidosis and stress doses of hydrocortisone (50–75 mg/m2 IV).
The adrenal cortex produces two main hormones: glucocortcoid (cortisol) and mineralocorticoid (aldosterone). AI is a clinical state that results from the inability of the adrenal cortex to produce these hormones in response to stress.
Primary AI results from congenital or acquired adrenal gland dysfunction. Secondary and tertiary AI result from pituitary or hypothalamic underfunction, respectively. Glucocorticoid deficiency impairs gluconeogenesis and glycogenolysis, and decreases the sensitivity of the vascular system to angiotensin II and norepinephrine, resulting in hypoglycemia, tachycardia, and mild hypotension. Aldosterone deficiency causes decreased sodium retention by the kidney, osmotic diuresis, hyponatremia, hypovolemia, and dehydration. In addition, it causes a decreased distal renal tubular exchange of potassium and hydrogen ions for sodium ions, leading to hyperkalemia and acidosis. Androgen deficiency in primary AI leads to ambiguous genitalia and underdeveloped secondary sexual characteristics in prepubertal children. In addition, in primary AI, the lack of negative feedback from cortisol on the anterior pituitary causes oversecretion of ACTH and propiomelanocortin that in turn stimulate skin hyperpigmentation (Fig. 77–1).
Pathophysiology of adrenal insufficiency.
The commonest cause of AI in North America is the abrupt withdrawal of glucocorticoids while on chronic treatment.1 Children who have been on glucocorticoid therapy for 2 to 4 weeks tend to have prolonged suppression of the hypothalamopituitary axis leading to secondary AI after treatment is stopped.2 The most common cause of primary AI in children is CAH, with an incidence of 1 in 10 000 to 18 000 live births.3 In long-term studies of children with AI, most have primary AI and, of these, approximately 72% are found to have CAH.4,5
CAH results from a deficiency in the enzymatic activity of one of the enzymes ...