Endometriosis affects girls and women from as young as eight to post menopause. The cause of endometriosis is not known with certainty, but a number of theories have been advanced. Research has shown that environmental toxins such as dioxin and PCBs, which act like hormones in the body and damage the immune system, can cause endometriosis.

In “endo,” as it is called for short, tissue like the endometrium is found outside the uterus, in other areas of the body. In these locations outside the uterus, the endometrial tissue develops into what are called “nodules,” “tumors,” “lesions,” “implants,” or “growths.” These growths can cause pain, infertility, and other problems.

The most common locations of endometrial growths are in the abdomen—involving the ovaries, fallopian tubes, the ligaments supporting the uterus, the area between he the vagina and the rectum, the outer surface of the uterus, and the lining of the pelvic cavity. Sometimes the growths are also found in abdominal surgery scars, on the intestines or in the rectum, or on the bladder, vagina, cervix, or vulva. Endometrial growths have also been found outside the abdomen, in the lungs, arms, thighs, and other locations, but these are uncommon. Like the lining of the uterus, endometrial growths usually respond to the hormones of the menstrual cycle.They build up tissue each month and then break down. The result is internal bleeding, degeneration of the blood and tissue shed from the growths, inflammation of the surrounding areas, and formation of scar tissue (adhesions).

For the latest information about endometriosis, visit the Endometriosis Association website.

Learn more about common overlapping conditions. Also contact other not-for-profit health organizations for more information about these related conditions.

Revised January 8, 2009