The major features of polycystic ovarian syndrome (PCOS) include menstrual dysfunction, anovulation, and signs of hyperandrogenism. Although the exact etiopathophysiology of this condition is unclear, PCOS can result from abnormal function of the hypothalamic-pituitary-ovarian (HPO) axis. A key characteristic of PCOS is inappropriate gonadotropin secretion, which is more likely a result of, rather than a cause of, ovarian dysfunction. In addition, one of the most consistent biochemical features of PCOS is a raised plasma testosterone level. A woman is diagnosed with polycystic ovaries (as opposed to PCOS) if she has 12 or more follicles in at least 1 ovary—measuring 2-9 mm in diameter—or a total ovarian volume greater than 10 cm3.