The ovaries, where a woman’s eggs are produced, have tiny fluid-filled sacs called follicles or cysts. As the egg grows, the follicle builds up fluid. When the egg matures, the follicle breaks open, the egg is released, and the egg travels through the fallopian tube to the uterus (womb) for fertilization. This is called ovulation.
In women with PCOS, the hormonal imbalance leads to improper egg development and maturation. The follicles start to grow and build up fluid but ovulation does not occur. Instead, some follicles enlarge and may remain as cysts. For these reasons, ovulation does not occur and the hormone progesterone is not made. Without progesterone, a woman’s menstrual cycle is irregular or absent. The ovaries also make male hormones, which prevent ovulation.