According to MedlinePlus, the exact cause of endometriosis is unknown, but one possible cause is a backward period flow, which is when cells travel backward through the fallopian tubes and into the pelvis during menstruation. Endometriosis can also run in families.
Endometriosis is a common condition that causes the lining of the uterus to grow in other areas of the body, including the ovaries, rectum, bowel, bladder and pelvic area. These growths stay inside of the body and generally cause multiple symptoms, including heavy bleeding, pain, bleeding between periods, and infertility, according to MedlinePlus. Because the cells that form these growths are from the uterus, they react to the hormones in the ovaries, which cause them to grow and bleed during menstruation.
Other symptoms of endometriosis include pain with bowel movements, pelvic or lower back pain, belly pain before, during and after periods, cramps up to two weeks before menstruation, and pain during and after sexual intercourse, notes MedlinePlus. The degree of discomfort varies in women with endometriosis. While some women may experience severe pain, women with a lot of pelvic tissue may not have any pain at all. Treatments for endometriosis include hormone therapy in the form of pills, sprays or shots or surgical procedures known as laparotomies or hysterectomies.