Endometriosis

Overview

The word “endometriosis” comes from the word “endometrium.” Endo means “inside,” and metrium means “uterus”. Healthcare providers call the tissue that lines the inside of the uterus the endometrium.

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

There is currently no cure for endometriosis, but there are effective treatment options for its symptoms. Researchers’ understanding of endometriosis continues to advance with new scientific evidence.

Signs and Symptoms

The most common symptoms of endometriosis are pain and infertility. Endometriosis pain can be severe, interfering with day-to-day activities.

Other common symptoms include:

• 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 periods
• Problems getting pregnant

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

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.

Related Health Effects

Infertility

Endometriosis is one of the top three causes of female infertility. Many women with fertility problems have endometriosis, but exactly how endometriosis causes infertility is not clear. Some evidence suggests infertility is related to the extent of the endometriosis patches, because the patches can distort the pelvic anatomy, making it difficult for sperm to travel to the ovary or a fertilized egg to travel to the uterus. Other evidence suggests inflammation in the abdomen may disrupt ovulation or fertilization, or that the endometrium may not develop properly, hampering the attachment of the embryo to the uterus.

Cancer Risk

Endometriosis and endometrial cancer are not the same. Endometriosis itself is not a form of cancer. There is a slight increase in the risk of ovarian cancer among women with endometriosis, particularly among women who were diagnosed with the condition at an early age. However, it is unclear whether endometriosis causes ovarian cancer or if the two conditions share risk factors or disease mechanisms that make them more likely to occur together. Some studies have found small links to other types of cancer, but the associations are much less clear.

Overlapping Pain Conditions

Studies have found a good deal of overlap among pain conditions. For instance, a woman may have endometriosis, irritable bowel syndrome, and depression at the same time—each of which may contribute to the overall pain she feels. Having more than one pain condition can complicate diagnosis and treatment.

Causes and Risk Factors

Researchers are not 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 do not explain every instance of endometriosis, such as endometriosis that occurs in organs like the lungs (possibly due to spreading through the blood system or lymphatics) or the rare cases of endometriosis in men.

Why Does Endometriosis Cause 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 always 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.

Current evidence suggests several possible explanations for pain associated with endometriosis:

• Patches of endometriosis respond to hormones in a way similar to 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 this 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.

Factors That May Increase Risk

Studies show that women are at higher risk for endometriosis if they:

• Have a mother, sister, or daughter with endometriosis
• Started their periods at an early age (before age 11)
• Have short monthly cycles (less than 27 days)
• Have heavy menstrual periods that last more than 7 days
• Are infertile

Some studies suggest that having a lean body mass or low body fat may increase a woman’s risk for endometriosis.

Factors That May Lower Risk

Studies also show that some factors may lower the risk for endometriosis, including:

• Periods that started late in adolescence
• Eating more than four servings per day of dairy foods during adolescence 
• Eating more fruit, especially citrus fruits
• Pregnancy
• Breastfeeding

After menopause, symptoms of endometriosis typically lessen because there is a drop in natural hormones and the growths gradually shrink. However, this is not true for all women. If a woman takes hormones for menopausal symptoms, both her pain symptoms and the growths may return.

Diagnosis

Surgery is currently the only way to confirm a diagnosis of endometriosis. The most common surgery is called laparoscopy.

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.

While laparoscopy is the most common surgery to check for endometriosis, sometimes a laparotomy (a surgical procedure involving a larger incision) is used to make a diagnosis.

Imaging Tests

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
• 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.

A healthcare provider will perform a laparoscopy only after learning a patient’s full medical history and giving a complete physical and pelvic exam. This information and exam, in addition to the results of an ultrasound or MRI, will help patients and their healthcare providers make more informed decisions about treatment.

Treatment and Management

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 a patient’s age, how severe the symptoms are, how severe the disease is, and whether the patient wants children.

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

Treatment options include hormone therapy, pain medicines, and surgical treatments.

Hormone Therapy

Because hormones cause endometriosis patches to go through a cycle similar to the menstrual cycle, hormones can be effective in treating endometriosis symptoms. Additionally, different hormones may alter perception of pain.

Hormone therapy is used to treat endometriosis-associated pain. Hormones come in the form of a pill, a shot or injection, or a nasal spray.

Hormone treatments stop the ovaries from producing hormones, including estrogen, and usually prevent ovulation. This may help slow the growth and local activity of both the endometrium and the endometrial lesions. Treatment also prevents new areas and scars (adhesions) from growing, but it will not make existing adhesions go away.

Healthcare providers may suggest one of the following hormone treatments to treat pain from endometriosis:

Gonadotropin-releasing hormone (GnRH) medicines stop the production of certain hormones to prevent ovulation, menstruation, and the growth of endometriosis, sending the body into a “menopausal” state.

• A GnRH medicine called elagolix is the first pill approved by the U.S. Food and Drug Administration (FDA) to treat pain associated with endometriosis.
  • The low-dose pill should not be taken for more than 24 months, and the high-dose pill should not be taken for more than 6 months, because it may cause bone loss.
  • The drug’s most common side effects include headache, nausea, difficulty sleeping, absence of periods, anxiety, depression, and joint pain.
• Some GnRH medicines come in a nasal spray taken daily, as an injection given once a month, or as an injection given every 3 months.
• Most healthcare providers recommend staying on GnRH medicine for only about 6 months at a time, with several months between treatments if they are repeated. The risk for heart complications and bone loss can rise when taking them longer. After stopping the GnRH medicine, the body comes out of the menopausal state, menstruation begins, and pregnancy is possible.
• As with all hormonal treatments, endometriosis symptoms return after women stop taking GnRH medicine.
• Side effects include hot flashes, tiredness, problems sleeping, headache, depression, joint and muscle stiffness, bone loss, and vaginal dryness.

Oral contraceptives, or birth control pills, help make a woman’s period lighter, shorter, and more regular. Women prescribed contraceptives also report relief from pain.

• In general, the therapy contains two hormones: estrogen and progestin, a progesterone-like hormone. Women who cannot take estrogen because of cardiovascular disease or a high risk of blood clots can use progestin-only pills to reduce menstrual flow.
• Typically, a woman takes the pill for 21 days and then takes sugar pills for 7 days to mimic the natural menstrual cycle. Some women take birth control pills continuously, without using the sugar pills that signal the body to go through menstruation. Taken without the sugar pills, birth control pills may stop the menstrual period altogether, which can reduce or eliminate the pain.
• Pain relief usually lasts only while taking the pills, while the endometriosis is suppressed. When treatment stops, the symptoms of endometriosis may return (along with the ability to get pregnant). Many women continue treatment indefinitely. Occasionally, some women have no pain for several years after stopping treatment.
• Mild side effects can include weight gain, bloating, and bleeding between periods, especially when women first start to take the pills continuously.

Progesterone and progestin, taken as a pill, by injection, or through an intrauterine device (IUD), improve symptoms by reducing a woman’s period or stopping it completely. This also prevents pregnancy.

• As a pill taken daily, these hormones reduce menstrual flow without causing the uterine lining to grow. As soon as a woman stops taking the progestin pill, symptoms may return, and pregnancy is possible.
• An IUD containing progestin may be effective in reducing endometriosis-associated pain. It reduces the size of lesions and reduces menstrual flow.
• As an injection taken every 3 months, these hormones usually stop menstrual flow.
• Women taking these hormones may gain weight, feel depressed, or have irregular vaginal bleeding.

Danazol treatment stops the release of hormones involved in the menstrual cycle. While taking this drug, women will have a period only occasionally or not at all.

• Common side effects include oily skin, acne, weight gain, muscle cramps, tiredness, smaller breasts, and sore breasts. Headaches, dizziness, weakness, hot flashes, or a deepening of the voice may also occur. Danazol’s side effects are more severe than those from other hormone treatment options.
• Danazol can harm a developing fetus. Therefore, it is important to prevent pregnancy while on this medicine. Hormonal birth control methods are not recommended for women taking danazol. Healthcare providers recommend using barrier methods of birth control, such as condoms or a diaphragm, while on this medicine.

Pain Medicines

Pain medicines may work well if pain or other symptoms are mild. These medicines range from over-the-counter pain relievers to strong prescription pain relievers. The most common types are nonsteroidal anti-inflammatory drugs, also called NSAIDs. Evidence on the effectiveness of these medicines for relieving endometriosis-associated pain is limited. Understanding which drugs relieve pain associated with endometriosis could also shed light on how endometriosis causes pain.

Surgical Treatments

Research shows that some surgical treatments can provide significant, although short-term, relief from endometriosis-related pain. Healthcare providers may recommend surgery to treat severe pain from endometriosis. During the operation, the surgeon can locate any areas of endometriosis and examine the size and degree of growth. They also may remove the endometriosis patches at that time. It is important to understand what is planned during surgery because some procedures cannot be reversed, and others can affect a woman’s fertility.

Laparoscopy is the most common surgical option. The surgeon inserts a small viewing instrument with a light, called a laparoscope, into the abdomen through a small cut to see the growths. To remove the endometriosis, the surgeon makes at least two more small cuts and inserts lasers or other surgical instruments to:

• Remove the lesions (excising)
• Destroy the lesions with intense heat and seal the blood vessels without stitches (cauterizing or vaporizing)

With surgery, most women have pain relief in the short term, but pain often returns. Surgery can provide long-term pain relief in women with deep lesions when those lesions are excised.

Laparotomy is a major abdominal surgery in which the surgeon may remove the endometriosis patches. However, sometimes the endometriosis lesions are too small to see in a laparotomy. During this procedure, the surgeon may also remove the uterus (hysterectomy). If the ovaries have endometriosis on them or if damage is severe, the surgeon may remove the ovaries and fallopian tubes along with the uterus. This process is called a total hysterectomy and bilateral salpingo-oophorectomy. When possible, healthcare providers will try to leave the ovaries in place because of the important role ovaries play in overall health. Healthcare providers recommend major surgery as a last resort for endometriosis treatment. Having a hysterectomy or salpingo-oophorectomy does not guarantee that the lesions will not return or that the pain will go away.

Surgery to sever pelvic nerves may be recommended if the pain is in the center of the abdomen. This can be done during either laparoscopy or laparotomy. However, the American College of Obstetricians and Gynecologists (ACOG) reports several clinical trials that showed these procedures to be ineffective at relieving pain from endometriosis, and these procedures are not currently included in ACOG recommendations for management of endometriosis.

Procedures used to sever different nerves in the pelvis:

• Presacral neurectomy severs the nerves connected to the uterus.
• Laparoscopic uterine nerve ablation (LUNA) severs nerves in the ligaments that secure the uterus.

In some cases, hormone therapy is used before or after surgery to reduce pain and continue treatment.

Treatments for Infertility Related to Endometriosis

In most cases, healthcare providers will recommend laparoscopy to remove or vaporize the growths to improve fertility in women who have mild or minimal endometriosis. Although studies show improved pregnancy rates following this type of surgery, the success rate is not clear.

If pregnancy does not occur after laparoscopic treatment, in vitro fertilization (IVF) may be the best option to improve fertility. IVF makes it possible to combine sperm and eggs in a laboratory to make an embryo, and the resulting embryos are placed into the woman’s uterus. It takes about two weeks to know whether the process is successful.

ACOG does not recommend using oral contraceptive pills or GnRH agonists to treat endometriosis-related infertility, as these hormonal agents prevent ovulation and delay pregnancy.

Surgery to remove the patches of tissue caused by endometriosis can improve a woman’s chances of getting pregnant, and some studies suggest that surgical treatment of endometriosis can double the pregnancy rate.

Living With Endometriosis

Women with endometriosis who are experiencing symptoms, especially after menopause, should talk with their healthcare providers about treatment options.

Some strategies may help women cope with pelvic pain related to endometriosis:

• Counseling or “talk therapy:” A mental health professional can help identify thoughts, feelings, and behaviors that may contribute to pain. Women with pain seem to have better treatment outcomes when counseling is added to medical treatment.
• Lifestyle changes: Some women’s pain is helped by changes in diet, improved posture, and regular physical activity.
• Physical therapy: Some types of pain respond well to physical therapy, which might involve massage, stretching, strengthening, or learning to relax or control pelvic muscles.

Describing your pain accurately and thoroughly may help your healthcare provider find the cause of the pain and treat it. Keeping a pain diary or record of your pain is a good way to track pain triggers as well as symptoms over time.

Some treatments for pelvic pain can affect a woman’s ability to get pregnant. For example, hormonal birth control is commonly used to treat endometriosis. Hysterectomy makes pregnancy impossible, but a woman may still be able to become a mother through other means, such as a surrogate carrier.

Find Clinical Trials

Clinical trials uncover better ways to prevent, diagnose, treat, and understand diseases and conditions. To ensure results apply to everyone, volunteers of all ages, sexes, and backgrounds, including both healthy individuals and those with specific medical conditions, are needed. Find clinical trials on endometriosis.

Find Treatment

The following organizations can help you find a healthcare provider or learn more about endometriosis:

• American College of Obstetricians and Gynecologists (ACOG): ACOG is the nation’s leading group of obstetricians and gynecologists (OB/GYNs) and other professionals providing healthcare for women. FAQ: Endometriosis
• American Society for Reproductive Medicine (ASRM): The ASRM is devoted to advancing knowledge and expertise in reproductive medicine and biology.
• Endometriosis: A Guide for Patients
• Womenshealth.gov: The HHS Office on Women’s Health promotes health equity for women and disseminates health information on topics of interest for women.

Community Support

The following groups study or provide information and support related to endometriosis:

• Endometriosis Association (EA) provides educational literature and support services and funds research on endometriosis, on the development of endometriosis, and treatments for the condition. EA educational brochures are available in more than 25 languages.
• Endometriosis.org is a global forum for news and information pertaining to medical treatments, surgical treatments, and emotional support for women who have endometriosis.
• Endometriosis Research Center (ERC) facilitates international endometriosis awareness, advocacy, support, education, legislative efforts, and supports research on endometriosis.
• World Endometriosis Society (WES) promotes the exchange of clinical and scientific knowledge among investigators committed to advancing the understanding of endometriosis to improve treatments and quality of life for women with the disease. WES is affiliated with the World Endometriosis Research Foundation: Fosters research into endometriosis to improve knowledge and treatments for this disorder.

Note: This resource list is for informational purposes only. It is not comprehensive, and an organization’s inclusion does not constitute an endorsement by NIH.  

Research Information

The National Institutes of Health (NIH) is the largest public funder of biomedical research in the world. NIH invests most of its budget in medical research seeking to enhance life and to reduce illness and disability. NIH-funded research has led to breakthroughs and new treatments helping people live longer, healthier lives, and building the research foundation that drives discovery.  

NIH research on endometriosis aims to understand the causes of and mechanisms for the condition, to identify and develop effective ways to treat pain and infertility related to endometriosis, and to find ways to prevent the condition. Researchers are also seeking less invasive ways to diagnose endometriosis.

Find NIH-funded research projects using NIH RePORTER, a searchable database of current and past research projects supported by NIH and other federal agencies.