Endocrinology of Hirsutism: From Androgens to Androgen Excess Disorders

Unwanted sexual hair growth has a considerable negative impact on a woman's self-esteem and quality of life. Excessive growth of terminal hair in women in a man-like pattern is defined as hirsutism and affects up to 1 in 7 women. Androgens secreted by the ovary and adrenal are the main regulator of physiological and pathological alterations of skin hair. Hirsutism is the result of the interaction between circulating serum androgens and hair follicles. Hirsutism is the most commonly used clinical diagnostic criterion of hyperandrogenism and majority of hirsutism cases are due to androgen excess. Over 80% of women with hirsutism will have polycystic ovary syndrome, about 10% will have idiopathic hirsutism, and the remaining will have rare disorders including non-classical congenital adrenal hyperplasia, hyperandrogenism with insulin resistance and acanthosis nigricans, and androgen-secreting neoplasms. Cushing's syndrome, acromegaly, thyroid dysfunction and hyperprolactinemia might be associated with hirsutism as well as the use of androgens, anabolic steroids and valproate. This paper provides an overview of the principal endocrinological aspects of hirsutism including the role of androgens in excessive hair growth and associated androgen excess disorders. Clinical evaluation and management of hirsutism are also discussed.