Polycystic ovary syndrome (PCOS) is a common hormonal disorder among women of reproductive age. The name of the condition comes from the appearance of the ovaries in most, but not all, women with the disorder - enlarged and containing numerous small cysts located along the outer edge of each ovary (polycystic appearance). Infrequent or prolonged menstrual periods, excess hair growth, acne and obesity can all occur in women with polycystic ovary syndrome. In adolescents, infrequent or absent menstruation may signal the condition. In women past adolescence, difficulty becoming pregnant or unexplained weight gain may be the first sign. The exact cause of polycystic ovary syndrome is unknown. Early diagnosis and treatment may reduce the risk of long-term complications, such as type 2 diabetes and heart disease.