The cells that normally line a woman’s uterus, called the endometrial tissues, are sensitive to the hormonal fluctuations associated with her menstrual cycles: Every thirty days or so these tissues go through a sequence of changes that involve thickening, sloughing and bleeding.

In some cases however, endometrial tissues begin growing outside the uterus, typically in the area around the ovaries, the bowel and/or the pelvic cavity lining. This condition is called endometriosis. 

In endometriosis, displaced tissues continue to be sensitive to hormonal fluctuations but there is no way for blood and other endometrial tissue products to exit the body. Surrounding tissues become irritated, develop scars and adhesions that can lead to severe pelvic pain and infertility. Indeed, it has been estimated that between 30 to 40 percent of women suffering from endometriosis are infertile. 

Endometriosis affects 5.5 million women in North America, or between two and ten percent of all North American women of reproductive age. Symptoms vary greatly among women diagnosed with the condition but can include: 

• Extremely heavy menstrual periods accompanied by severe, disabling menstrual cramps
• Chronic pain in the region of the pelvis and lower back
• Dyspareunia
• Painful bowel movements and urination during menstrual periods
• Diarrhea
• Infertility
• Breakthrough bleeding

The Causes of Endometriosis

The exact cause of endometriosis is unknown. Scientists have several theories.

Retrograde Menstruation

Some of the tissue sloughed off during a woman’s menstrual flow travels backwards through the fallopian tubes and into the abdominal cavity. In most women, the immune system prevents this sloughed tissue from attaching to the peritoneal surface. Medical scientists have theorized, however, that in some women, this sloughed tissue is able to implant itself, leading to the development of endometriosis. Why does this happen in some women but not in others? Retrograde menstruation theorists are not entirely sure but posit hereditary factors, toxins, a compromised immune system or some combinatio0n of the three. 

Embryonic Development 

Another theory hypothesizes that potentially endometrial cells may migrate outside the uterus during embryonic development. These cells are activated when a woman reaches puberty. When these cells detach from the endometrial mantle, they can initiate the development of endometrial colonies elsewhere in the body as well.

Heredity

Women who have a close family member with endometriosis are about ten times more likely than the population at large to be diagnosed with endometriosis themselves. There may be a genetic cause for endometriosis.

Endometrial Transplantation 

There are cases where endometrial cells have been found inside surgical incisions – made while the patient was being operated on for endometriosis. Theoretically then, endometrial cells could be carried by blood or the lymphatic system to various parts of the body.

Environmental Exposure

The University of Utah is participating in an ongoing study attempting to see whether the presence of certain environmental chemicals can be linked to the incidence of endometriosis. Patients undergoing surgery to remove endometrial growth will have their tissues tested for the presence of certain trace chemicals. So far these women have been found to have much higher concentrations of dioxins and PCBs in their tissues than the female population at large.