Endometriosis afflicts one in 25 women in the United States—among them, film star Marilyn Monroe. That means that for these women, the endometrium, which is supposed to be inside the uterus is not. When endometriosis patients ovulate, the endometrium thickens, despite being misplaced; when they menstruate, the lining is not properly shed and remains trapped inside the body. This can lead to pain and scarring and form cysts, and the dead tissue creates a risk of infection. In addition, the cells can connect organs that are not supposed to be connected. At least a third of women with endometriosis have fertility problems, either because the misplaced uterine lining provides no place for implantation to occur, because scarring prevents conception, or because cellular chemicals are released that interfere with fertilization or gestation.
Endometriosis pain follows no known pattern. It may occur during menstruation, or mid-cycle, both, or at random. Pain can also happen during bowel movements, urination, or intercourse. People can have severe pain despite relatively mild endometriosis, and a severe form of the condition may not be associated with a great deal of pain. Other symptoms of the condition include heavy periods, bleeding between periods, constipation, diarrhea, or bloating.
The case of the illness is unclear. The predominant hypothesis is a condition called retrograde menstruation, in which some menstrual blood goes the wrong way into the stomach or fallopian tubes and leaves bits of endometrium which are then not removed by the immune system. However, why the immune system is ineffectual in these cases, and why retrograde menstruation happens in the first place, are not well understood. Another theory suggests that cells existing within the abdominal cavity change to resemble uterine cells—also for no clear reason—and these then spread there. Although endometriosis is not present from birth or menarche, there is some evidence that it runs in families. Women with short cycles or who have never given birth are particularly at risk.
When there is no fertility issue, treatment is generally focused on management, using hormone therapy or even just pain medication. When there are fertility problems that need to be addressed, surgery may be necessary. If the uterus is severely damaged, a hysterectomy might be needed to protect the patient’s overall health.