What is polycystic ovary syndrome? Polycystic ovary syndrome (PCOS) is a common endocrine and metabolic disease. The main characteristic is that multiple follicles develop in the ovaries, but they cannot mature to ovulate, leading to hormone imbalance, cycle disorders, infertility, obesity, increased hair and other problems. In recent years, PCOS has received increasing attention. What causes polycystic ovary syndrome? At present, the cause of PCOS is not very clear. It may be a combination of genetic factors, living habits, environmental factors, drugs and other factors.