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Endometriosis and PCOS: What’s the Difference?

Posted on March 11, 2021
Medically reviewed by
Peter J. Chen, M.D.
Article written by
Annie Keller

Endometriosis and polycystic ovary (or ovarian) syndrome (PCOS) are both gynecological conditions affecting the reproductive system. They can cause problems with menstruation and infertility. Although they share some symptoms, they are separate conditions with different causes and treatments. Here’s what’s specific to each condition and what they have in common.

Differences in Causes

In both endometriosis and PCOS, the direct cause of the symptoms is known, but it is still unknown why those symptoms develop in some women but not in others.

Endometriosis is a condition in which the tissue that lines the uterus grows elsewhere in the pelvic cavity. It is currently not known why the tissue grows in those other places. There are several different theories regarding what causes endometriosis. In metaplasia, body tissues change from one type to another. This may happen before birth, in an embryo, or may happen later in life. The normal tissues that line the pelvic cavity would change into endometrial tissue.

A similar theory is the induction theory — when hormones or other immune responses cause cells in the abdomen to change into endometrial cells. A third theory is the cell transport theory. Endometrial cells travel from the uterus through blood or lymphatic tissue and implant in the pelvic cavity. It is at least partially hereditary. Women with endometriosis are more likely to have daughters with the condition.

Polycystic ovary syndrome is a hormonal condition in which the body produces excessive amounts of a hormone called androgen. PCOS is often accompanied by insulin resistance, in which the body cannot use the insulin it makes to break down sugars and regulate blood sugar. Insulin resistance can lead to weight gain.

Another hormone, progesterone, is deficient and leads to irregular periods. Genetics is believed to play a role in whether women develop PCOS. Although obesity or overweight may be a characteristic of women with PCOS, it should not be considered as a factor. It may be a sign or result of PCOS.

Differences in Symptoms

Endometriosis and PCOS both cause irregularities in the menstrual cycle. One MyEndometriosisTeam member wrote, “I have both endo and PCOS, so sometimes I don’t know what to do or what is causing what symptoms.” Both may cause heavy periods. Beyond that, there are several differences.

There are several common symptoms of endometriosis. The most common is pelvic pain, especially during the menstrual cycle. This may be directly from painful periods (dysmenorrhea) or may be separate. Back pain or pain in the lower abdomen may occur during menstruation or ovulation. You may also have pain during urination or while having a bowel movement. Other gastrointestinal problems, like nausea, constipation, or diarrhea, can also result. There can be pain during sex, usually felt deep inside the body and not at the entrance to the vagina.

The main symptom of PCOS is irregular periods. Excessive amounts of androgen can produce certain physical signs, like excess facial and body hair growth, male-pattern baldness, and serious cases of acne.

Complications in Endometriosis and PCOS

PCOS and endometriosis are among the most common causes of infertility. Other complications of the two conditions differ.

Infertility in Endometriosis and PCOS

Endometriosis is one of the most common causes of infertility. One study done by the American Society for Reproductive Medicine found that at least 25 percent and up to 50 percent of all women who reported infertility were later diagnosed with endometriosis.

Infertility is the most common complication of PCOS. The hormonal imbalances can lead to ovulation ceasing, and if a woman no longer ovulates, she cannot get pregnant.

Other Endometriosis Complications

Other complications of endometriosis are less well-defined. There is an increased rate of ovarian cancer in women with endometriosis, but ovarian cancer is still rare even in these women. An extremely rare cancer, endometriosis-associated adenocarcinoma, occasionally develops in women who have had endometriosis for some time.

Other PCOS Complications

Insulin resistance is common in PCOS and can eventually lead to type 2 diabetes. Women with PCOS are also more likely to develop gestational diabetes. Other complications with PCOS include an increased risk of heart disease, high blood pressure, and sleep apnea. If women with PCOS develop a thickening of the lining of the uterus (endometrium) called endometrial hyperplasia, they are at an increased risk for endometrial cancer.

Differences in Diagnosis

Ultrasound technology can help diagnose both endometriosis and PCOS, but it isn’t a definitive diagnostic tool for either condition.

Unless there is visible endometrial tissue in the vagina, there is only one way to diagnose endometriosis — laparoscopic surgery (surgery to explore the contents of the abdomen). Ultrasound may be used to see if there are endometriomas (cysts associated with endometriosis), but it cannot diagnose endometriosis on its own. “PCOS can show up during ultrasounds. Mine did. But my endo didn’t. That can only be done [by] laparoscopy,” one member explained.

There are no tests that can definitively tell if someone has PCOS. A physical exam is the first step to getting a diagnosis. Your doctor will look to see if you have any of the common symptoms of PCOS. Blood tests are used to check for insulin resistance, hormone levels, high cholesterol, and triglycerides. An ultrasound is used to look for cysts in the ovaries and any sign of endometrial hyperplasia.

Differences in Treatments

Both endometriosis and PCOS do not have any cures. Treatment of endometriosis is usually symptom-based, and treatment of PCOS is primarily symptom-based. If a woman has no symptoms that are causing her pain or other difficulties, watchful waiting is used. This means the condition is periodically monitored to see if it progresses. Endometriosis and PCOS can be treated with hormonal medications.

Because the primary symptom of endometriosis is pelvic pain, the first lines of treatment include pain relief. Nonsteroidal anti-inflammatory drugs (NSAIDs) may be prescribed. Physiotherapy can be used to strengthen pelvic muscles. Tricyclic antidepressants are used to modify the perception of pain, and transcutaneous electrical nerve stimulator (TENS) units can be applied to the affected area. They send electrical impulses to block pain or produce endorphins to fight pain.

Endometriosis can also be treated through hormonal methods. Because endometrial tissue grows when exposed to estrogen, methods that block the production of estrogen can reduce symptoms. These range from hormonal birth control to medications based on testosterone.

Surgery is an option for treating endometriosis if the treatments above are not enough. This can range from ablation or removal of deposits of endometrial tissue to removal of the ovaries (oophorectomy) and/or uterus (hysterectomy). One member mentioned surgery as being the only real treatment she found for her condition. “For me, two excision surgeries were the start of true healing.”

PCOS has a variety of treatments that differ from endometriosis. Lifestyle changes such as weight loss are usually recommended to ease symptoms. To ease hormonal symptoms, combination birth control pills and progestin therapy are prescribed to regulate the menstrual cycle. Metformin, a drug used for type 2 diabetes, is prescribed to reduce insulin resistance.

Is It Possible to Have Endometriosis and PCOS?

It is possible to have both endometriosis and PCOS. There is not a lot of research on the subject, but one 2014 study found that 12 percent of women with PCOS also had endometriosis. Because 5 percent to 10 percent of women are believed to have one or the other, there is potentially more overlap than is currently known.

Find Support

MyEndometriosisTeam is the social network for women with endometriosis and their loved ones. The platform is home to more than 113,000 members who offer support and share their unique experiences. Many members are living with endometriosis and PCOS.

Are you dealing with both PCOS and endometriosis? Do you suspect you may have one or the other? Comment below or start a conversation on MyEndometriosisTeam.

Peter J. Chen, M.D. is a fellow of the American College of Obstetrics and Gynecology. Review provided by VeriMed Healthcare Network. Learn more about him here.
Annie Keller specializes in writing about medicine, medical devices, and biotech. Learn more about her here.

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