Why does PCOS cause problems with the menstrual cycle?
A normal menstrual cycle is dependent upon regular cyclic changes in the blood hormone levels of estrogen and progesterone. These hormones are produced in the ovaries. A woman’s ovaries have follicles, which are tiny sacs filled with liquid that hold the eggs. Each month about 20 eggs start to mature, but usually only one becomes dominant. The growing follicle produces the hormone estrogen. As the one egg grows, the follicle accumulates fluid in it. When that egg matures, the follicle breaks open to release the egg so it can travel through the fallopian tube for fertilization. When the single egg leaves the follicle, ovulation takes place. After ovulation occurs, the remainder of the ruptured follicle in the ovary produces progesterone. This is the process that occurs normally on a monthly basis in women with regular menstrual cycles. In women with PCOS, the ovary doesn’t make all of the hormones it needs for any of the eggs to fully mature. They may start to grow and accumulate fluid.
