The different types of adrenogenital syndrome are inherited as autosomal recessive diseases and can affect both boys and girls. The defect is lack of an enzyme needed by the adrenal gland to make the major steroid hormones of the adrenal cortex: cortisol and aldosterone. Due to the block in synthesis of these hormones, there is abnormal 'feedback' and steroids are 'diverted' to becoming androgens, a form of male sex hormones. This causes early appearance of male characteristics.

In a newborn girl with this disorder, the clitoris is enlarged with the urethral opening at the base (ambiguous genitalia, often appearing more male-like than female). The internal structures of the reproductive tract (ovaries, uterus, and fallopian tubes) are normal. As she grows older, masculinization of some features takes place, such as deepening of the voice, the appearance of facial hair, and failure to menstruate at puberty.

In a newborn boy no obvious abnormality is present, but long before puberty normally occurs, the child becomes increasingly muscular, the penis enlarges, pubic hair appears, and the voice deepens. Affected males may appear to enter puberty as early as 2-3 years of age. At puberty, the testes are small.

Some forms of congenital adrenal hyperplasia are more severe and cause adrenal crisis in the newborn due to salt wasting. In this salt-losing form of congenital adrenal hyperplasia, newborns develop symptoms shortly after birth. These include vomiting, dehydration, electrolyte changes, and cardiac arrhythmias. Untreated, this condition can lead to death within 1-6 weeks after birth.

About 1 in 10,000 to 18,000 children are born with congenital adrenal hyperplasia.