Polycystic ovary syndrome (PCOS) is an inherited disease that affects women of childbearing age. The disorder causes multiple abnormal cysts in enlarged ovaries, so that they do not produce the normal number of eggs and do not ovulate (release eggs) normally. The disease is present at birth but does not cause symptoms until women enter puberty. PCOS occurs in up to 10% of women and is a leading cause of female infertility. Women with PCOS have irregular and infrequent menstrual periods and may develop amenorrhea (complete absence of menstrual periods). Women with PCOS are likely to have high blood pressure, obesity (especially central obesity, around the midsection of the abdomen), facial acne, hirsutism (excessive facial and body hair growth), and thinning scalp hair. They also have insulin resistance, which may lead to development of type 2 diabetes. The February 7, 2007, issue of JAMA includes an article about polycystic ovary syndrome.