Endometriosis and adenomyosis both cause abnormal growth of tissue similar to the uterine lining. They can cause similar symptoms such as pelvic pain, unusual menstrual bleeding, and heavy periods.

While endometriosis causes the tissue to grow outside the uterus, adenomyosis causes it to grow into the uterine muscle. A person can have both conditions at once.

Because the symptoms are so similar, the conditions can be difficult to diagnose — even healthcare professionals may have difficulty distinguishing one from the other. This is especially true of endometriosis, which requires surgery to definitively diagnose. On average, people with endometriosis wait nearly 7 years for a diagnosis.

Both conditions often respond well to hormonal birth control, so a doctor may recommend this as the first line of treatment if they suspect that a person has adenomyosis or endometriosis.

Read on to learn about the conditions, their similarities and differences, symptoms, prevalence, causes, and more.

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Both adenomyosis and endometriosis cause abnormal growth of tissue similar to the endometrium, the tissue that lines the inside of the uterus.

In adenomyosis, the tissue overgrows, extending into the muscle of the uterus. However, in endometriosis, the tissue grows outside the uterus, often attaching to nearby structures such as the ovaries and fallopian tubes.

This tissue secretes substances such as prostaglandins and inflammatory chemicals that can cause pain. Although the tissue does not line the uterus, it swells and bleeds during menstrual cycles just as the endometrium does. This can be painful and harmful.

Adenomyosis and endometriosis have some common symptoms. Both conditions can cause:

  • pelvic pain, especially during a person’s period
  • unusual bleeding patterns such as very long, irregular, or missed periods
  • heavy periods
  • infertility and subfertility

Additionally, adenomyosis may cause a person’s uterus to soften and enlarge, which can make the abdomen feel swollen.

Endometriosis can cause varied symptoms depending on where the endometrial tissue grows. For example, endometrial tissue can adhere to digestive organs, causing stomach pain or bowel dysfunction.

Learn more about the symptoms of endometriosis and adenomyosis.

Doctors do not know the exact prevalence of endometriosis. This is because people with the condition often do not receive a diagnosis for many years, and surgery is the only way to definitively diagnose it. This means that the actual number of people with endometriosis may be much higher than current estimates.

Most estimates suggest that 10–15% of reproductive-age people with uteruses have the condition. Among those with pelvic pain, the prevalence may be as high as 70%.

Similar issues of under-reporting and underdiagnosis exist for adenomyosis.

Adenomyosis is more common among people who have had a dilation and curettage (D&C) — a procedure for pregnancy termination — and treatment for some miscarriages. Research suggests an overall prevalence of 20–35%.

Researchers do not fully understand what causes either condition.

One of the most widely accepted explanations for endometriosis is retrograde menstruation. This theory suggests that during a person’s period, some of the menstrual flow travels backward through the fallopian tubes, allowing the tissue a person sheds during their period to move elsewhere in their body.

As for adenomyosis, researchers believe that a disruption in the boundary between the uterine muscle and the deepest layer of the endometrial tissue may cause the condition. This is why injuries and surgery can be risk factors.

However, both conditions are estrogen-dependent, which means they can occur only when estrogen levels are high enough to allow the endometrial tissue to grow.

The risk factors for endometriosis include:

  • a family history of endometriosis
  • menstruation that starts before age 11
  • monthly cycles shorter than 27 days
  • heavy periods lasting longer than 7 days
  • infertility
  • lean body mass or low body fat

The risk factors for adenomyosis include:

  • increased exposure to estrogen, such as from starting periods at an early age or having many pregnancies
  • higher body mass
  • use of oral contraceptives
  • a history of uterine surgeries
  • use of the medication tamoxifen

A doctor may suspect endometriosis, adenomyosis, or both depending on a person’s symptoms.

Imaging tests such as pelvic ultrasound and magnetic resonance imaging (MRI) can help doctors diagnose adenomyosis. These tests may also help rule out other potential causes of pelvic pain if a doctor suspects endometriosis.

While imaging scans may suggest that a person has endometriosis, the only way to conclusively diagnose the condition is through surgery to examine the uterus.

The right treatment depends on a person’s symptoms, overall health, and fertility goals.

If a person does not want to become pregnant but wishes to preserve future fertility, the following medications can help with both endometriosis and adenomyosis:

  • nonsteroidal anti-inflammatory drugs (NSAIDs) for pain
  • oral contraceptives
  • the androgen-increasing drug danazol

When a person wants to become pregnant, they can stop taking these medications. A person may also need fertility treatments to become pregnant. These may include drugs to induce ovulation and therapies such as intrauterine insemination (IUI) and in vitro fertilization (IVF).

People with endometriosis who do not want to become pregnant may try taking a gonadotropin-releasing hormone (GnRh), usually for a short trial of 3 months. This can shrink the endometrial tissue and reduce symptoms.

Surgery to remove endometrial adhesions or adenomyosis growths may be helpful if the medication does not work.

A hysterectomy is the only way to permanently cure adenomyosis. However, in many cases, surgery and medical treatments work well to manage symptoms, so a hysterectomy is not necessary.

A hysterectomy may help reduce endometriosis symptoms but will not necessarily cure endometriosis.

Endometriosis has no cure.

While surgery can reduce the symptoms, various studies note recurrence rates of 6–67% after surgery. In 5–59% of people who undergo medical treatment for endometriosis, pain persists.

Pregnancy is possible in people with endometriosis, but rates of pregnancy complications are higher and a person may have more difficulty getting and staying pregnant.

The prognosis for adenomyosis varies.

More adenomyosis adhesions, especially very deep ones, usually correlate with worse symptoms. Doctors typically start with medication and, depending on the results, may then try more invasive treatments.

A hysterectomy can cure adenomyosis, but without a uterus, a person cannot carry a pregnancy. People who want to have children after a hysterectomy can consider using a gestational carrier or surrogate to carry a pregnancy for them.

Adenomyosis and endometriosis cause similar symptoms, and a person can have both conditions at the same time.

Treatments for the two conditions are similar, so if a doctor is uncertain which condition a person has, they may start by recommending birth control or other hormonal medications. If a person does not experience relief from the first-line treatments, it can be helpful for them to see a specialist for additional guidance.