dermatologic disorders
Hirsutism and Hypertrichosis
Pathophysiology of Hirsutism and Hypertrichosis
Hair growth depends on the balance between androgens (eg,testosterone, dehydroepiandrosterone sulfate [DHEAS], dihydrotestosterone [DHT]) andestrogens. Androgens promote thick, dark hair growth.Testosteronestimulates hair growth in the pubic area and underarms. Dihydrotestosterone stimulates beard hair growth and scalp hair loss. Hirsutism can be due to an Increase in circulating androgen levels Enhanced end organ response to androgens Hirsutism typically results from abnormally high androgen levels as a result of increased production of androgens (eg, due to ovarian or adrenal disorders) or increased peripheral conversion oftestosteroneto DHT by 5-alpha-reductase. Free androgen levels also can increase as a result of decreased production of sex hormone–binding globulin, which can occur in a variety of conditions, including hyperinsulinemia, hyperprolactinemia, and in androgen excess itself. However, the severity of hirsutism does not correlate with the level of circulating androgens because of individual differences in androgen sensitivity of the hair follicle. Hirsutism also may be the result of increased end organ response to normal plasma levels of androgens and manifest as a familial phenomenon in people of Mediterranean, South Asian, or Middle Eastern ancestry. Hirsutism in pregnancy and menopause is due to temporary, physiologic fluctuations in androgen levels. When caused by increased androgen levels, hirsutism is often accompanied by virilization, which may manifest as loss of menses, increased muscle mass, voice deepening, acne, Etiology , and clitoromegaly. Hypertrichosis involves nonandrogenic hair growth. 