An ovarian cyst is a sac filled with fluid that forms on or inside an ovary.
This article is about cysts that form during your monthly menstrual cycle, called functional cysts.
Functional cysts are not the same as cysts caused by cancer or other diseases. The formation of these cysts is a perfectly normal event and is a sign that the ovaries are working well.
Each month during your menstrual cycle, a follicle (cyst) grows on your ovary. The follicle is where an egg is developing.
• The follicle makes the estrogen hormone. This hormone causes normal changes of the uterine lining as the uterus prepares for pregnancy.
• When the egg matures, it is released from the follicle. This is called ovulation.
• If the follicle fails to break open and release an egg, the fluid stays in the follicle and forms a cyst. This is called a follicular cyst.
Another type of cyst occurs after an egg has been released from a follicle. This is called a corpus luteum cyst. This type of cyst may contain a small amount of blood. This cyst releases progesterone and estrogen hormones.
Ovarian cysts are more common in the childbearing years between puberty and menopause. The condition is less common after menopause.
Taking fertility drugs often causes the development of multiple follicles (cysts) in the ovaries. These cysts most often go away after a woman’s period, or after a pregnancy.
Functional ovarian cysts are not the same as ovarian tumors or cysts due to hormone-related conditions such as polycystic ovary syndrome.