What is endometriosis?

Endometriosis is a disease that affects women, mainly during their reproductive years.

The same tissue lining the inside of the uterus (womb) establishes itself in sites of the body other than the uterus – mostly, within the pelvis. If a sample of the endometriosis tissue is taken and sent to a pathologist, under the microscope it has exactly the same appearance as the internal lining (endometrium) of the uterus. This means it functions in much the same way, growing through the cycle in response to the ovarian hormones and then shedding some of its tissue and also bleeding at the time of the period.

Obviously, the amount of blood loss from any particular patch or spot of endometriosis will depend on how much tissue is present. Endometriosis can therefore occur in tiny spots no larger than a pinhead, but can vary in size from these to masses larger than a cricket ball. Fortunately, minor endometriosis, which involves very small amounts of abnormal tissue, is more common than very severe levels of disease where very large amounts of endometriosis tissue are present.

Endometriosis and the ovulation cycle

In the normal female menstrual cycle, the internal lining of the uterus (endometrium) is very hormone responsive. The appearance of the tissue on any particular day of the cycle is dependent upon which ovarian hormone, or combination of ovarian hormones, is affecting it. Therefore, in the first half of any one cycle the lining of the uterus grows rapidly; in the second half it begins to secrete mucous, compact and organise itself to receive a pregnancy, and during the menstrual phase of the cycle the tissue sheds off and bleeds quite freely.

Endometriosis tissue, due to its abnormal site and blood supply, is sometimes a little less responsive than the normal endometrium, but it essentially undergoes the same changes. The most damaging of these is the bleeding, which occurs at the time of the period. Menstrual-type blood can therefore be released into sites in which it was never meant to occur, such as inside the pelvis.

This release of menstrual-type blood explains many of the side effects and symptoms that are associated with endometriosis. The hormone responsiveness of endometriosis also explains why we can use sometimes hormone therapy to treat the disease.

By interrupting the constant ebb and flow of ovarian hormones to the endometriosis, we are able to disrupt the course of the disease and prevent it from growing or spreading and, in many cases; we are able to get rid of it entirely.