Estrogen and progesterone are the female hormones produced by the ovaries. These hormones cause monthly menstrual cycles to occur. These hormones also help eggs to develop in follicles, which are fluid-filled pockets, before an egg is released each month to travel down the fallopian tube.
A third hormone, testosterone, also is produced by the ovaries in small amounts. Testosterone is in a broad class of hormones called androgens, and it is the dominant sex hormone in men. Between 4% and 7% of women produce too much testosterone in their ovaries. These women have a pattern of symptoms called polycystic ovary syndrome.
When a woman has a high level of androgen hormones such as testosterone in her body, she can be unable to release eggs from their follicles in the ovaries. Since the fluid-filled follicles don't open and empty, they stay in the ovary and the ovaries appear to contain many cysts. This is the reason for the term "polycystic" in the name of the disease. Women with this condition may have problems with fertility because egg release (ovulation) stops or happens only once in a while. When no egg is released during a monthly cycle, the woman's hormones don't change levels as they normally should. In reaction, the uterus manufactures a fragile inside lining that can cause her to have irregular bleeding. The lining is not shed all at once as during a normal menstrual period. Because of the abnormal hormone balance, the lining of the uterus is also at a higher risk of developing a cancer.
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