Congenital adrenal hyperplasia (CAH), also termed adrenogenital syndrome in older literature, is a common inherited form of adrenal insufficiency.
Adrogenital syndrome is a group of diseases is due to mutations (genetic defects) in the genes coding for several enzymes needed for the production of adrenal cortex hormones. About 95% of cases are caused by 21-hydroxylase deficiency. This enzyme is necessary for efficient production of two vital adrenal steroid hormones: cortisol and aldosterone. Deficient production of these substances causes disruption in the delicate balance of hormones. Sensing low levels of cortisol, the adrenal, directed by the master hypothalamus and pituitary glands, goes into high gear. Because cortisol production is impeded, the adrenal cortex instead manufactures androgens, or male steroid hormones, an undesired by-product. In short, while one part of the adrenal functions poorly, making inadequate amounts of cortisol and aldosterone, another portion of the gland over-produces androgens. This last feature distinguishes CAH-21-hydroxylase deficiency from Addison's disease, since in Addisonian patients, the adrenals are most often completely non-functional.