Endometriosis

Endometriosis is a disease in which tissue similar to the lining of the uterus grows in other places in the body. It is one of the most common gynecological diseases, and its primary symptoms include pain and infertility.

NICHD conducts and supports research to improve understanding of the mechanisms, diagnosis, and treatments of endometriosis.

About Endometriosis

Endometriosis is a disease in which tissue similar to the lining of the uterus grows in other places in the body.

The word endometriosis comes from the word “endometrium”—endo means “inside,” and metrium means “uterus,” where a mother carries her baby. Healthcare providers call the tissue that lines the inside of the uterus the endometrium.

Researchers aren’t exactly sure what causes endometriosis, but some theories include the following:

  • Retrograde menstruation. This theory proposes that endometriosis cells flow backward through the fallopian tubes and into the pelvis during menstruation.
  • Coelomic metaplasia. This theory refers to a change in the characteristics of the cells that line the organs in the pelvis.

These theories don’t explain every instance of endometriosis, like endometriosis that occurs in organs such as the lungs (possibly due to spreading through the blood system or lymphatics) or the rare cases of endometriosis in men.

Healthcare providers may use the terms “implants,” “nodules,” or “lesions” to describe areas or patches of endometriosis. Most endometriosis patches are found in the pelvic cavity:

  • On the ovaries
  • On the fallopian tubes, which carry egg cells from the ovaries to the uterus
  • Behind the uterus
  • On the tissues that hold the uterus in place
  • On the bowels or bladder

In rare cases, endometriosis may grow outside the pelvic cavity, such as on the lungs or in other parts of the body.1

The female reproductive organs are shown with red patches of endometriosis located on the ovaries and on the outside of the uterus. The uterus, fallopian tubes, ovaries, vagina, and areas of endometriosis are labeled.

Researchers’ understanding of endometriosis is changing with new scientific evidence. For example, researchers used to think that pain from endometriosis was related to the size of the patches growing outside the uterus. But evidence shows this is not the case. In fact, the size and location of the lesions are not related to the severity or to the location of the pain.2,3 Studies also indicate that pain is not associated with a woman’s ability to get pregnant.4,5

Citations

  1. Office on Women’s Health, U.S. Department of Health and Human Services. (2019). Endometriosis. Retrieved October 10, 2019, from https://www.womenshealth.gov/a-z-topics/endometriosis
  2. Stratton, P., & Berkley, K. J. (2011). Chronic pelvic pain and endometriosis: Translational evidence of the relationship and implications. Human Reproduction Update, 17(3), 327–346. Retrieved February 11, 2020, from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3072022/
  3. American College of Obstetricians and Gynecologists. (2010, reaffirmed 2018). Practice Bulletin No. 114: Management of endometriosis. Obstetrics & Gynecology, 116(1), 223–236. Retrieved February 11, 2020, from https://journals.lww.com/greenjournal/Citation/2010/07000/Practice_Bulletin_No__114__Management_of.41.aspx external link
  4. Santulli, P., Bourdon, M., Presse, M., Gayet, V., Marcellin, L., Prunet, C., et al. (2016). Endometriosis-related infertility: Assisted reproductive technology has no adverse impact on pain or quality-of-life scores. Fertility and Sterility, 105(4), 978–987. Retrieved February 11, 2020, from https://www.sciencedirect.com/science/article/pii/S0015028215021755?via%3Dihub external link
  5. Wilson-Harris, B. M., Nutter, B., & Falcone, T. (2014). Long-term fertility after laparoscopy for endometriosis-associated pelvic pain in young adult women. Journal of Minimally Invasive Gynecology, 21(6), 1061–1066. Retrieved February 11, 2020, from https://www.sciencedirect.com/science/article/pii/S155346501400288X?via%3Dihub external link

What are the risk factors for endometriosis?

Research shows that certain factors may increase or decrease a woman’s risk for endometriosis.

Citations

  1. American College of Obstetricians and Gynecologists (ACOG). (2019). Endometriosis. Retrieved October 10, 2019, from https://www.acog.org/Patients/FAQs/Endometriosis external link
  2. ACOG. (2010, reaffirmed 2018). Practice Bulletin No. 114: Management of endometriosis. Obstetrics & Gynecology, 116(1), 223–236. Retrieved February 11, 2020, from https://journals.lww.com/greenjournal/Citation/2010/07000/Practice_Bulletin_No__114__Management_of.41.aspx external link
  3. Peterson, C. M., Johnstone, E. B., Hammoud, A. O., Stanford, J. B., Varner, M. W., Kennedy, A., et al. (2013). Risk factors associated with endometriosis: Importance of study population for characterizing disease in the ENDO Study. American Journal of Obstetrics and Gynecology208(6), 451.e1–451.11. Retrieved February 11, 2020, from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4114145/
  4. Treloar, S. A., Bell, T. A., Nagle, C. M., Purdie, D. M., & Green, A. C. (2010). Early menstrual characteristics associated with subsequent diagnosis of endometriosis. American Journal of Obstetrics and Gynecology, 202(6), 534.e1–534.e6. Retrieved February 11, 2020, from https://www.sciencedirect.com/science/article/abs/pii/S0002937809019802?via%3Dihub external link
  5. Farland, L. V., Eliassen, A. H., Tamimi, R. M., Spiegelman, D., Michels, K. B., & Missmer, S. A. (2017). History of breast feeding and risk of incident endometriosis: Prospective cohort study. BMJ (Clinical research ed.)358, j3778. Retrieved February 11, 2020, from https://www.bmj.com/content/358/bmj.j3778 external link
  6. Harris, H. R., Eke, A. C., Chavarro, J. E., & Missmer, S. A. (2018). Fruit and vegetable consumption and risk of endometriosis. Human reproduction (Oxford, England)33(4), 715–727. Retrieved February 11, 2020, from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6018917/
  7. Farland, L. V., Missmer, S. A., Bijon, A., Gusto, G., Gelot, A., Clavel-Chapelon, F., et al. (2017). Associations among body size across the life course, adult height, and endometriosis. Human reproduction (Oxford, England), 32(8), 1732–1742. Retrieved February 11, 2020, from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5850750/

What are the symptoms of endometriosis?

The most common symptoms of endometriosis are pain and infertility.1

Other common symptoms of endometriosis include:1

  • Painful or even debilitating menstrual cramps, which may get worse over time
  • Pain during or after sex
  • Pain in the intestine or lower abdomen
  • Painful bowel movements or painful urination during menstrual periods
  • Heavy menstrual periods
  • Premenstrual spotting or bleeding between periods2
  • Problems getting pregnant3

In addition, women with endometriosis may have painful bladder syndrome, digestive or gastrointestinal symptoms similar to a bowel disorder, as well as fatigue or lack of energy.4, 5

For some women, the pain associated with endometriosis gets milder after menopause. However, hormone therapy, such as estrogen or birth control pills given to reduce menopausal symptoms, may cause the pain and other symptoms to continue.

Endometriosis-Related Pain

Researchers know that pain is a primary symptom of endometriosis, but they do not know exactly what causes the pain.

The severity of the pain does not correspond with the number, location, or extent of endometriosis lesions. Some women with only a few small lesions experience severe pain; other women may have very large patches of endometriosis but experience little pain.1,6

Current evidence suggests several possible explanations for pain associated with endometriosis, including the following:1,6

  • Patches of endometriosis respond to hormones in a similar way as the lining of the uterus. These tissues may bleed or have inflammation every month, like a regular menstrual period. However, the blood and tissue shed from endometriosis patches stay in the body and are irritants, which can cause pain.
  • In some cases, inflammation and chemicals produced by the endometriosis areas can cause the pelvic organs to stick together, causing scar tissue. This makes the uterus, ovaries, fallopian tubes, bladder, and rectum appear as one large organ.
  • Hormones and chemicals released by endometriosis tissue may irritate nearby tissue and cause it to release other chemicals that cause pain.
  • Over time, some endometriosis areas may form nodules or bumps on the surface of pelvic organs or become cysts (fluid-filled sacs) on the ovaries.
  • Some endometriosis lesions have nerves in them, tying the patches directly into the central nervous system. These nerves may be more sensitive to pain-causing chemicals released in the lesions and surrounding areas. Over time, they may be more easily activated by the chemicals than normal nerve cells are.
  • Patches of endometriosis might also press against nearby nerve cells to cause pain.
  • Some women report less endometriosis pain after pregnancy, but the reason for this is unclear. Researchers are trying to determine whether the pain reduction results from the hormones the body releases during pregnancy or from changes in the cervix, uterus, or endometrium that occur during pregnancy and delivery.

Endometriosis pain can be severe, interfering with day-to-day activities. Understanding how endometriosis is related to pain is a very active area of research because it could allow for more effective treatments for this type of pain.

Citations

  1. American College of Obstetricians and Gynecologists. (2019). Endometriosis. Retrieved October 11, 2019, from https://www.acog.org/Patients/FAQs/Endometriosis external link
  2. Heitmann, R. J., Langan, K. L., Huang, R. R., Chow, G. E., & Burney, R. O. (2014). Premenstrual spotting of ≥2 days is strongly associated with histologically confirmed endometriosis in women with infertility. American Journal of Obstetrics and Gynecology, 211(4), 358.e1–358.e3586. Retrieved January 23, 2020, from https://www.ncbi.nlm.nih.gov/pubmed/?term=24799313
  3. NICHD. (2018). Spotlight: What to know about endometriosis. Retrieved January 23, 2020, from https://www.nichd.nih.gov/newsroom/resources/spotlight/031218-spotlight-endometriosis
  4. Surrey, E. S., Soliman, A. M., Johnson, S. J., Davis, M., Castelli-Haley, J., & Snabes, M. C. (2018). Risk of developing comorbidities among women with endometriosis: A retrospective matched cohort study. Journal of Women’s Health, 27(9), 1114–1123. Retrieved November 1, 2019, from https://www.ncbi.nlm.nih.gov/pubmed/30070938
  5. Ramin-Wright, A., Kohl Schwartz, A. S., Geraedts, K., Rauchfuss, M., Wölfler, M. M., Haeberlin, F., et al. (2018). Fatigue - a symptom in endometriosis. Human Reproduction, 33(8), 1459–1465. Retrieved November 1, 2019, from https://www.ncbi.nlm.nih.gov/pubmed/29947766
  6. Stratton, P., & Berkley, K. J. (2011). Chronic pelvic pain and endometriosis: Translational evidence of the relationship and implications. Human Reproduction Update, 17(3), 327–346. Retrieved February 11, 2020, from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3072022/

How do healthcare providers diagnose endometriosis?

Surgery is currently the only way to confirm a diagnosis of endometriosis.

The most common surgery is called laparoscopy.

In this procedure:

  • The surgeon uses an instrument to inflate the abdomen slightly with a harmless gas.
  • After making a small cut in the abdomen, the surgeon uses a small viewing instrument with a light, called a laparoscope, to look at the reproductive organs, intestines, and other surfaces to see if there is any endometriosis.
  • If patches of tissue are present, the surgeon examines them to determine whether they are endometriosis and, if so, at what stage they might be.
  • In some cases, the surgeon will also do a biopsy, which involves taking a small tissue sample and studying it under a microscope, to confirm the diagnosis.1
  • The most common surgery is a laparoscopy, but sometimes a laparotomy—a surgical procedure involving a larger incision—is used to make a diagnosis.

Healthcare providers may also use imaging methods to produce a “picture” of the inside of the body. Imaging allows them to locate larger endometriosis areas, such as nodules or cysts. The two most common imaging tests are ultrasound, which uses sound waves to make the picture, and magnetic resonance imaging (MRI), which uses magnets and radio waves to make the picture. These types of imaging do not help diagnose small lesions or adhesions.1

Your healthcare provider will perform a laparoscopy only after learning your full medical history and giving you a complete physical and pelvic exam. This information and exam, in addition to the results of an ultrasound or MRI, will help you and your healthcare provider make more informed decisions about treatment.

Researchers are also seeking less invasive ways to diagnose endometriosis and determine how severe it is. NICHD-funded researchers in the National Centers for Translational Research in Reproduction and Infertility created a “diagnostic classifier” for endometriosis based on the presence of particular genes. The classifier was 90% to 100% accurate. Once the classifier is validated, a simple biopsy in the doctor’s office may be a nonsurgical way to diagnose endometriosis in most women.2

Citations

  1. American College of Obstetricians and Gynecologists. (2010, reaffirmed 2018). Management of endometriosis. Practice Bulletin No. 114. Washington, DC. Retrieved February 11, 2020, from https://insights.ovid.com/article/00006250-201007000-00041 external link
  2. Tamaresis, J. S., Irwin, J. C., Goldfien, G. A., Rabban, J. T., Burney, R. O., Nezhat, C., et al. (2014). Molecular classification of endometriosis and disease stage using high-dimensional genomic data. Endocrinology, 155(12), 4986–4999. Retrieved February 11, 2020, from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4239429/

What are the treatments for endometriosis?

There is currently no cure for endometriosis, but there are treatment options for related pain and infertility.

Healthcare providers consider several factors when determining the best treatment for endometriosis symptoms, including:

  • Your age
  • How severe your symptoms are
  • How severe the disease is
  • Whether you want children

Not all treatments work well for all women with endometriosis. Also, endometriosis symptoms may return after the treatment is stopped or, in the case of surgery, as more time passes after the procedure.

Citations

  1. American College of Obstetricians and Gynecologists. (2010, reaffirmed 2018). Practice Bulletin No. 114: Management of endometriosis. Obstetrics & Gynecology, 116(1), 223–236. Retrieved February 11, 2020, from https://journals.lww.com/greenjournal/Citation/2010/07000/Practice_Bulletin_No__114__Management_of.41.aspx external link
  2. American College of Obstetricians and Gynecologists. (2019). Endometriosis. Retrieved October 13, 2019, from https://www.acog.org/Patients/FAQs/Endometriosis external link
  3. Giudice, L. C. (2010). Endometriosis. New England Journal of Medicine, 362(25), 2389–2398. Retrieved February 11, 2020, from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3108065/
  4. Struthers, R. S., Nicholls, A. J., Grundy, J., Chen, T., Jimenez, R., Yen, S. S., & Bozigian, H. P. (2009). Suppression of gonadotropins and estradiol in premenopausal women by oral administration of the nonpeptide gonadotropin-releasing hormone antagonist elagolix. Journal of Clinical Endocrinology and Metabolism, 94(2), 545–551. Retrieved October 28, 2019, from https://www.ncbi.nlm.nih.gov/pubmed/19033369
  5. U.S. Food and Drug Administration. (2018). Drug Trials Snapshots: ORILISSA. Retrieved October 28, 2019, from https://www.fda.gov/drugs/drug-approvals-and-databases/drug-trials-snapshots-orilissa
  6. Limonta, P., Marelli, M. M., Moretti, R., Marzagalli, M., Fontana, F., & Maggi, R. (2018). Chapter two - GnRH in the human female reproductive axis. In G. Litwack (Ed.), Vitamins and hormones (Vol. 107, pp. 27–66). Cambridge, MA: Academic Press. Retrieved November 1, 2019, from https://www.sciencedirect.com/science/article/pii/S0083672918300037 external link
  7. Practice Committee of the American Society for Reproductive Medicine. (2014). Treatment of pelvic pain associated with endometriosis: A committee opinion. Fertility and Sterility, 101(4), 927–935. Retrieved February 11, 2020, from https://www.sciencedirect.com/science/article/pii/S0015028214001502?via%3Dihub external link
  8. Yeung, P. P., Jr., Shwayder, J., & Pasic, R. P. (2009). Laparoscopic management of endometriosis: Comprehensive review of best evidence. Journal of Minimally Invasive Gynecology, 16(3), 269–281. Retrieved February 11, 2020, from https://www.sciencedirect.com/science/article/pii/S1553465009001113?via%3Dihub external link
  9. U.S. Food and Drug Administration. (2002). Depo-Provera® Contraceptive Injection. Retrieved January 27, 2020, from https://www.accessdata.fda.gov/drugsatfda_docs/label/2003/20246scs019_Depo-provera_lbl.pdf (PDF 152 KB)
  10. Stratton, P., & Berkley, K. J. (2011). Chronic pelvic pain and endometriosis: Translational evidence of the relationship and implications. Human Reproduction Update, 17(3), 327–346. Retrieved February 11, 2020, from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3072022/
  11. Hughes, E., Brown, J., Collins, J. J., Farguhar, C., Fedorkow, D. M., & Vandekerckhove, P. (2007). Ovulation suppression for endometriosis. Cochrane Database of Systematic Reviews, (3), Art. No. CD000155. Retrieved February 11, 2020, from https://www.cochrane.org/CD000155/MENSTR_ovulation-suppression-for-endometriosis external link
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