CausesBy Mayo Clinic staff
Most ovarian cysts start during the normal function of your menstrual cycle. These are known as functional cysts. Other types of cysts are much less common.
Your ovaries normally grow cyst-like structures called follicles each month. Follicles produce the hormones estrogen and progesterone and release an egg when you ovulate. Sometimes a normal monthly follicle just keeps growing. When that happens, it becomes known as a functional cyst. There are two types of functional cysts:
- Follicular cyst. Around the midpoint of your menstrual cycle, an egg bursts out of its follicle and begins its journey down the fallopian tube in search of sperm and fertilization. A follicular cyst begins when something goes wrong and the follicle doesn't rupture or release its egg. Instead it grows and turns into a cyst.
Corpus luteum cyst. When a follicle does release its egg, the ruptured follicle begins producing large quantities of estrogen and progesterone in preparation for conception. This changed follicle is now called the corpus luteum. Sometimes, however, the escape opening of the egg seals off and fluid accumulates inside the follicle, causing the corpus luteum to expand into a cyst.
The fertility drug clomiphene (Clomid, Serophene), which is used to induce ovulation, increases the risk of a corpus luteum cyst developing after ovulation. These cysts don't prevent or threaten a resulting pregnancy.
Functional cysts are usually harmless, rarely cause pain, and often disappear on their own within two or three menstrual cycles.
Some types of cysts are not related to the normal function of your menstrual cycle. These cysts include:
- Dermoid cysts. These cysts may contain tissue such as hair, skin or teeth because they form from cells that produce human eggs. They are rarely cancerous.
- Cystadenomas. These cysts develop from ovarian tissue and may be filled with a watery liquid or a mucous material.
- Endometriomas. These cysts develop as a result of endometriosis, a condition in which uterine endometrial cells grow outside your uterus. Some of that tissue may attach to your ovary and form a growth.
Dermoid cysts and cystadenomas can become large, causing the ovary to move out of its usual position in the pelvis. This increases the chance of painful twisting of your ovary, called ovarian torsion.
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