Appearance of male external sexual characteristics in a girl or woman. This takes place under the influence of male sex hormones (androgens). The clitoris becomes enlarged, and hair distribution resembles a man’s (hirsutism), with hair on the chest and face. The voice deepens, the breasts either do not develop or become smaller, and menstruation does not occur. A female baby with excess androgens can look just like a boy at birth. The clitoris looks like a penis and the labia may have shrunk. This may happen if the mother is taking medication containing androgens or if the baby girl has a disorder of the adrenal cortex. The production of androgens in the adrenal cortex is then increased because of the absence of an enzyme (congenital adrenogenital syndrome). When the disorder is contracted at a later date it is known as the acquired adrenogenital syndrome. The cause is then usually an androgen-producing tumour in the adrenal cortex. In an enzyme disorder treatment consists of hormone therapy. Any tumour (benign or malignant) is removed. Treatment causes most signs of virilism to disappear, although male hair distribution and an enlarged clitoris often remain. Cosmetic removal of the hair, and correction of clitoris size by plastic surgery, are both possible.