Hyperandrogenism in peripubertal girls. Androgens arise from either adrenal or ovarian secretion or by peripheral conversion of secreted precursors. The adrenals and ovaries normally contribute about equally to testosterone and AD production. DHAS is the major adrenal 17-KS. Testosterone is the major circulating form of androgen. More than 96% of plasma testosterone is bound to SHBG; the free testosterone seems to be the bioavailable fraction. Hyperandrogenism must be considered in any girl with premature or excessive development of public hair or acne, menstrual irregularity (whether it be oligo-amenorrhea or dysfunctional uterine bleeding), or obesity. The most common cause of premature public hair development (pubarche) is premature adrenarche. The most common cause of hyperandrogenism presenting in a teenage girl is polycystic ovary syndrome. However, the differential diagnosis includes "exaggerated adrenarche," late-onset congenital adrenal hyperplasia, virilizing tumors, Cushing's syndrome, hyperprolactinemia, acromegaly, and abnormalities of androgen action or of metabolism. The plasma free testosterone is a more sensitive indicator of hyperandrogenism than is the total testosterone concentration. The pattern of response of plasma free testosterone, DHAS, and cortisol to dex-suppression testing is diagnostic of the source of androgen excess. Most hyperandrogenic adolescents will be found to have PCOS. The treatment is chosen according to particular symptoms, such as menstrual irregularity, hirsutism, or obesity. 