In women with polycystic ovary syndrome, the ovary doesn’t make all of the hormones it needs for an egg to fully mature. The follicles may start to grow and build up fluid, but ovulation does not occur. Instead, some follicles 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. Plus, the ovaries produce male hormones, which also prevent ovulation.