Polycystic ovary syndrome (PCOS) is an endocrine system disorder where small fluid-filled sacs develop on the ovaries. PCOS affects women in their reproductive years. Learn about PCOS, a hormone problem that affects the ovaries and can cause missed periods, excess hair growth, acne, and infertility. Find out the causes, symptoms, diagnosis, treatment, and complications of PCOS. Polycystic ovary syndrome (PCOS) is a major public health problem affecting ~11–13% of women worldwide. In this Primer, Stener-Victorin et al. review the epidemiology and pathophysiology of PCOS ... Many women with polycystic ovarian syndrome are unaware they have it. Learn more about symptoms, treatment, and tips to help keep your ovaries healthy.