Congenital adrenal hyperplasia (CAH) refers to a group of diseases associated with either complete (classical form) or partial (non-classical) anomalies in the biosynthesis of adrenal hormones. The prevalence of the classical form associated with 21-hydroxylase deficiency has been estimated at 1/14,000. However, the non-classical forms are more common. The disease is characterized by insufficient production of cortisol, or of aldosterone (classical form with salt wasting), associated with overproduction of adrenal androgens. In the classical form, metabolic decompensation (dehydration with hyponatremia, hyperkalemia and acidosis associated with mineralocorticoid deficiency, and hypoglycemia associated with glucocorticoid deficiency) may be life-threatening from the neonatal period onwards. Genital anomalies may be noted at birth in affected females. Chronic hyperandrogenism may lead to accelerated growth during childhood, but advanced bone maturation may lead to a deficit in final height. Adults tend to be overweight and metabolic disturbances, bone anomalies and fertility problems may also be present. Non-classical forms are associated with later onset, during the peri- or postpubertal period, and manifest with signs of hyperandrogenism (acne, hirsutism, menstrual problems and infertility). CAH is transmitted as an autosomal recessive trait. The most common form (accounting for 95% of cases) results from 21-hydroxylase deficiency. Other causes of CAH include deficiencies of 11-hydroxylase, 3-beta-hydroxysteroid dehydrogenase or 17-alpha-hydroxylase. Newborn screening for 21-hydroxylase deficiency (classical form) has been established in many countries and is based on measurement of 17-hydroxyprogesterone levels. Identification of an index case should lead to testing of all family members and relatives. Prenatal diagnosis is possible through molecular analysis of fetal DNA and allows treatment to be established for preventing virilization in affected females. Life-long hormone replacement therapy (gluco- and mineralocorticoids for the classical forms with salt wasting, and glucocorticoids for the simple virilizing forms) requires close follow-up (pediatric through to adulthood) and has improved the prognosis for patients by preventing complications associated with chronic hyperandrogenism and allowing normal fertility. Genital anomalies in females may require surgical intervention(s).
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