The cause or causes of endometriosis are unclear. We do know, however, that it is not caused by cancer or a pelvic infection. In cases of endometriosis, the uterine tissue spreads to organs outside the uterus, including the fallopian tubes, bowels, bladder and, in rare cases, the lungs. In some cases, abdominal lining changes into endometrial cells. Outside the uterus, these cells act the same way they would inside—every month, the tissue breaks down and bleeds, except in this case, it has nowhere to go, so the tissue and old blood builds up, causing inflammation, scarring and swelling.
There are a number of theories about the causes of endometriosis. One is retrograde menstruation, in which some of the tissue a woman sheds during menstruation flows into her pelvis after backing up through the fallopian tubes. However, while some women with retrograde menstruation develop endometriosis, not all do.
Other researchers believe genetics or familial history is to blame. The condition could either be inherited or there could be some genetic errors that cause it to develop. Still others link the condition to hormones and the endocrine system; in particular, estrogen appears to promote endometriosis. It’s also possible that the immune systems of women with endometriosis do not properly remove menstrual fluid from the pelvic cavity. There is also research into whether exposure to manmade chemicals provokes the condition.
This condition can affect all women—those with children and those who have never given birth, from their first period through menopause, regardless of race, ethnicity or socioeconomic status. It can sometimes continue after menopause, or perhaps, the hormones taken to relieve menopause symptoms may cause the symptoms of endometriosis to persist.