Progesterone

Progesterone is a female hormone produced by the corpus luteum (the empty follicle) after ovulation, responsible for preparing and maintaining the uterine lining for potential pregnancy and regulating the second half of the menstrual cycle. Women with PCOS characteristically have low or absent progesterone because anovulation—the failure to ovulate—means the corpus luteum never forms, leaving the uterine lining exposed to constant estrogen stimulation without progesterone's balancing and protective effects. This unopposed estrogen increases the risk of irregular or heavy bleeding, endometrial hyperplasia, and over time, endometrial cancer, making cycle regulation through ovulation restoration or progesterone supplementation an important part of PCOS management.