According to the United States Department of Health and Human Services, the condition may affect more than 11% of women between ages 15 and 44. Still, many women are confused or embarrassed about their symptoms or feel ashamed of their diagnosis, says Mamie McLean, MD, assistant professor of obstetrics and gynecology at the University of Alabama Birmingham.
Here’s what Dr. McLean wants every woman to know about this debilitating—but often very treatable—condition.
It starts when tissue grows in the wrong place
Endometriosis occurs when the endometrium—the tissue that lines the inside of a woman’s uterus—begins to grow in places it shouldn’t: the ovaries, fallopian tubes, and the lining of the pelvis, for example. (In rare cases, it can grow in other organs throughout the body, as well.)
But endometrial tissue doesn’t function like tissue in the rest of the body. Because it’s involved in menstruation, it thickens, breaks down, and bleeds once a month or so. And that continues to happen, no matter where the tissue is in the body.
In the uterus, broken down endometrial tissue leaves the body each month during a woman’s period. In other parts of the body, it becomes trapped and can irritate surrounding tissues and organs.
It can be extremely painful—or completely painless
When this happens, cysts (called endometriomas) and scar tissue can form. For many women, this can cause severe pain—during their periods, during sex, or during bowel movements or urination. They might also experience symptoms such as heavy bleeding, fatigue, diarrhea, constipation, bloating, or nausea during their periods.
But the disease is different for everyone, says Dr. McClean, and scientists’ understanding of how it affects pain sensation is still poorly understood.
“We’ll see patients who have very advanced disease and lots of scar tissue, and they had no idea they had this condition,” she says. “Either they’ve had no pain, or they figured it was normal and learned to live with it. For others, they’ll have very minimal disease and very severe pain.”
It’s a common cause of infertility
Scarring and tissue growth in the ovaries can make it difficult for a woman to get pregnant. “The normal process by which the sperm travels up the fallopian tube to meet the egg simply can’t happen, because there’s too much structural distortion,” says Dr. McClean.
Even if the sperm is able to get through, she adds, underlying inflammation can sometimes lead to poor implantation or poor egg quality.
She does note, however, that not everyone with endometriosis has trouble conceiving—so if a woman is not trying to get pregnant, she should always use protection even if she does have the disease.
It may be caused by “retrograde menstruation”
Doctors don’t know exactly what causes endometriosis, or why certain women are affected. In many cases, doctors think it has something to do with “retrograde menstruation,” when blood containing endometrial cells flows backward into the abdominal cavity rather than out of the body.
“Most women are able to absorb that tissue,” says Dr. McClean. “But in some women, due to immune circumstances or genetic circumstances that we don’t really understand yet, that tissue can implant inside the abdomen and lead to many of these symptoms.”
In any case, endometriosis is not caused by anything a woman did or could have prevented. “That’s what feels so frustrating about this condition,” says Dr. McClean. “When I tell a woman that her ability to conceive will be very challenging and there’s nothing she could have done differently, it really feels like an unfair situation you’re simply just born into.”
Treatments do work for many women
Endometriosis is a chronic condition, and there is no absolute cure, says Dr. McClean. But for many women, treatments can relieve pain and discomfort, improve fertility, and help them live normal lives.
Depending on the severity of endometriosis and its symptoms, treatments can vary from pain medications and hormonal therapies (like birth control pills) to surgery. Women who want to get pregnant may also need to use assistive reproductive technology, such as in vitro fertilization.
Surgery for endometriosis can range from laparoscopic “keyhole” procedures, in which endometrial tissue is cut away or burned with a laser, to a full hysterectomy. For many women, surgery will greatly reduce pain and symptoms. But for about 20% of patients, endometriosis will come back.
Unfortunately, says Dr. McClean, some women do require multiple surgeries—and each subsequent surgery is less likely to solve the problem. “It’s often the first surgery that gives the best relief,” she says.
“Each additional surgery tends to increase your risk of complications and decrease the reward in terms of reduction in pain,” she adds. Complications, especially for women who have had repeat procedures, can include bowel injury, pelvic infection, or damage to blood vessels or nerves.
Other therapies can help too
Therapies today are able to attack endometriosis from hormonal, musculoskeletal, and neurological standpoints, says Dr. McClean, and an experienced physician can help women find the combination of treatments that best addresses their symptoms and needs. This could include medication, surgery, and even pelvic physical therapy.
Dr. McClean recommends that any woman who’s struggling with pelvic pain that’s bad enough to limit their daily activities seek an evaluation from her doctor.
“Women take it very personally when they have a condition or disease that causes this kind of pain or may limit their ability to have children,” she says. “But I think with National Infertility Awareness Week and the availability of support groups—and with celebrities like Lena Dunham speaking publicly about their experiences—more women are now talking about it and getting the help they need."
This post was originally published on May 4, 2017 and has been updated for accuracy.