Polycystic ovaries. Magnetic resonance imaging (MRI) scan of a female patient with polycystic ovary syndrome (PCOS). PCOS, also known as Stein- Leventhal syndrome, is caused by hormone imbalances and results in multiple cysts (white) forming in the ovaries (centre left and right). A cyst is an abnormal fluid-filled cavity. Ovarian cysts can form when follicles fail to ovulate. Symptoms of PCOS are irregular or absent menstruation (amenorrhoea), obesity, acne, and excessive bodily hair (hirsuitism). Treatment includes hormone regulation, such as using oral contraceptive pills, and surgical removal of the cysts.