Many women experience problems with their periods. But for up to 10 percent of women, the problems can be caused by an increasingly common condition called polycystic ovary syndrome (PCOS). Some of the characteristics of PCOS include elevated levels of testosterone and/or related hormones called androgens (hyperandrogenism), infrequent or prolonged menstrual periods (anovulation), and/or the presence of multiple ovarian cysts that may be seen on ultrasound.