Heavy Bleeding & Pelvic Pressure in Perimenopause: Is It Adenomyosis?

Experiencing heavy periods, pelvic pressure, or bloating in your 40s? Dr. Karen Tang & Dr. Haver explain adenomyosis symptoms and how to get answers.

Adenomyosis can cause heavy periods, worsening menstrual pain, pelvic pressure, and bloating. These symptoms can become particularly confusing during perimenopause, when periods and hormone levels are already changing.

“Adenomyosis is probably the most common [condition] that no one's ever heard of,” says Karen Tang, MD, MPH, a board-certified gynecologist and minimally invasive gynecologic surgeon and author of It’s Not Hysteria: Everything You Need to Know About Your Reproductive Health (but Were Never Told).

Dr. Tang joined Mary Claire Haver, MD, FACOG, CMP, a board-certified OB-GYN, Certified Menopause Practitioner, and adjunct professor of obstetrics and gynecology at the University of Texas Medical Branch, for the unPAUSED episode Endometriosis and Fibroids Don’t Stop at Menopause with Dr. Karen Tang.

Their conversation focuses on a question that matters for women entering perimenopause: What happens to gynecologic conditions that were already present when reproductive hormones begin to change? With adenomyosis, the answer can include changes in bleeding and pain, symptoms that can overlap with the menopause transition itself.

As Dr. Haver puts it, “Heavy bleeding in perimenopause deserves more than ‘your hormones are changing.’ Adenomyosis is one possible explanation, and many women do not hear the word until they are diagnosed.”

Key Takeaways: Adenomyosis at a Glance

• Definition: A gynecologic condition where endometrial-like tissue grows into the muscular wall of the uterus (myometrium).
• Primary Symptoms: Unusually heavy or prolonged menstrual bleeding, worsening pelvic pain/cramping, pelvic pressure, bloating, and pain during sex.
• Adenomyosis vs. Endometriosis: Adenomyosis occurs inside the uterine wall; endometriosis occurs outside the uterus on external organs.
• Impact on Perimenopause: Fluctuating estrogen levels during perimenopause may trigger unpredictable flare-ups in bleeding and pain, often misdiagnosed as "normal hormonal shifts."
• Diagnosis: Evaluated through clinical history, transvaginal ultrasound, or MRI showing a heterogeneous myometrium or enlarged uterus.

What is adenomyosis?

Adenomyosis is a non-cancerous gynecologic condition where endometrial-like tissue grows into the myometrium (the muscular wall of the uterus). It can cause very heavy menstrual bleeding, painful periods, pelvic pressure, bloating, and other pelvic symptoms.

Dr. Tang describes adenomyosis and endometriosis as “cousins.” They involve similar types of tissue growing in different places. Endometriosis involves endometrial-like tissue growing outside the uterus. With adenomyosis, endometrial-like tissue grows within the uterine muscle.

“Picture the uterus as a pear. The flesh represents the muscular wall of the uterus. The area around the seeds represents the uterine cavity, which is lined by the endometrium. With adenomyosis, endometrial-like tissue grows into that fleshy muscular wall,” Dr. Tang says.

That location helps explain why adenomyosis can affect the size and appearance of the uterus as well as menstrual bleeding.

What are the symptoms of adenomyosis?

Common adenomyosis symptoms include heavy or prolonged periods, increasingly painful periods, pelvic pain or pressure, bleeding between periods, pain during sex, and bloating, and even bowel and bladder symptoms. 

Heavy bleeding and pain with periods are probably the most classic symptoms, however. “People start to bleed very, very heavily, almost uncontrollably,” Dr. Tang explains. “And they can have really bad pain.”

Some women continue to have predictable periods, but the amount of bleeding becomes much heavier. Others experience increasingly irregular bleeding or worsening pain. That can be especially difficult to recognize during perimenopause because menstrual changes are already common during this stage.

“During perimenopause these changes may be dismissed as ‘just hormones’ even when another condition is contributing,” says Dr. Haver. A major change in bleeding or pain deserves attention, particularly when the symptoms are new, worsening, or interfering with daily life.

Not everyone with adenomyosis experiences symptoms, however. Some women learn they have the condition only after imaging or an evaluation for another concern.

What happens to adenomyosis symptoms during perimenopause?

Adenomyosis symptoms can overlap with the menstrual changes of perimenopause, making it harder to know what is driving new or worsening bleeding and pelvic pain.

Dr. Tang describes estrogen during perimenopause as fluctuating rather than a steady decline. Ovulation also becomes inconsistent, which means progesterone exposure varies from cycle to cycle.

For a woman with adenomyosis, that can make symptoms unpredictable. One month might bring very heavy bleeding and significant pain. Another may be relatively uneventful.

The practical takeaway is to pay attention to a change from your own baseline. If periods suddenly become much heavier or more painful, or pelvic and bowel symptoms begin interfering with daily life, Dr. Tang recommends talking with a gynecologist. Imaging may help identify adenomyosis, fibroids, or another gynecologic condition.

Dr. Haver makes the point directly: “Heavy bleeding in perimenopause deserves more than ‘your hormones are changing.’”

Adenomyosis is one possible explanation. Fibroids, endometriosis, and the changing cycles of perimenopause can produce overlapping symptoms, which is why figuring out what is driving the bleeding or pain may require a closer evaluation.

Adenomyosis vs. endometriosis: What is the difference?

The main difference between adenomyosis and endometriosis is where the endometrial-like tissue grows. Adenomyosis occurs within the muscular wall of the uterus. Endometriosis occurs outside the uterus.

Dr. Tang explains that adenomyosis may produce recognizable changes on imaging. The uterine muscle may look less uniform, which clinicians may describe as a “heterogeneous myometrium.” Imaging can also show small pockets of blood within the muscle, changes at the border between the uterine cavity and muscle, or an enlarged, rounded uterus.

Endometriosis can be much harder to see on routine imaging. Women with endometriosis can have ultrasound, CT, or MRI results that appear normal. This difference is one reason the two conditions can follow different paths to diagnosis.

How is adenomyosis diagnosed?

Diagnosing adenomyosis usually means putting several pieces together: symptoms, bleeding pattern, uterine history, physical examination, and imaging. Ultrasound is often the first imaging test, with MRI sometimes used when additional detail is needed.

Here are several findings clinicians may see on imaging:

• A heterogeneous, or uneven-looking, uterine muscle (a.k.a. A heterogenous myometrium) 

• Small pockets of blood within the uterine muscle

• A less distinct border between the uterine cavity and muscle

• An enlarged or rounded uterus

These findings can suggest adenomyosis, but no single finding confirms the diagnosis. Clinicians consider imaging results alongside symptoms, medical history, and other clinical findings. Symptoms can also overlap with fibroids, endometriosis, and perimenopausal bleeding changes. That makes the medical history especially valuable.

“Your uterine history may matter, too,” says Dr. Haver. “If your symptoms changed after a C-section, D&C, fibroid removal, or another uterine procedure, say so. That timing may help explain what is happening.”

Heavy bleeding, worsening pain, pelvic pressure, bloating, changes in bleeding pattern, and the timing of symptoms in relation to a uterine procedure are all useful information to share with a gynecologist.

“Heavy bleeding or worsening pain deserves a real evaluation,” Dr. Haver says.

What causes adenomyosis?

Researchers are still trying to understand exactly what causes adenomyosis. They believe several factors may be involved, including changes or injury where the uterine lining meets the muscle, estrogen activity, inflammation, genetics, and certain cells that may contribute to tissue growth.

What makes adenomyosis difficult to explain is that researchers know what happens in the uterus, but they don't fully understand why. In women with adenomyosis, tissue similar to the uterine lining grows into the muscular wall of the uterus. How that tissue gets there, and why it happens in some women but not others, is still being studied.

There are several theories about how adenomyosis develops. Here's what researchers think may be happening.

Uterine Injury & Repair

One of the leading theories centers on the boundary between the endometrium, the inner lining of the uterus, and the myometrium, the muscular uterine wall. This area is sometimes called the endometrial-myometrial interface or junctional zone.

The theory proposes that injury or repeated disruption in this area may allow cells from the endometrium to move into the uterine muscle. Once there, these cells may contribute to the development of adenomyosis. Research often refers to this proposed process as “tissue injury and repair.” .

“C-sections is the big one,” says Dr. Tang when discussing risk factors that contribute to adenomyosis. She also points to D&Cs and surgeries that involve cutting into the uterus to remove fibroids.

There is normally a boundary separating the uterine cavity from the muscle. One theory is that disrupting this area during a uterine procedure could make it possible for endometrial-like tissue to grow into the muscle.

Prior uterine surgery has been associated with adenomyosis in some research, but this does not mean a C-section, D&C, or fibroid surgery will cause adenomyosis. It also doesn't establish that tissue injury is the explanation for every case. A 2023 review specifically examining the tissue injury and repair theory concluded that more evidence is needed before it can be accepted as a single explanation for how adenomyosis develops. 

Inward Cell Growth a.k.a. Endometrial Invagination

A closely related theory proposes that cells from the deepest layer of the endometrium gradually grow, or “invaginate,” into the myometrium, the muscular wall of the uterus.

This is one of the most widely discussed explanations for adenomyosis. Genetic research offers some support for it. Researchers have identified some of the same acquired genetic changes, including mutations involving the KRAS gene, in adenomyosis tissue and nearby endometrial glands. This suggests that at least some adenomyosis lesions may originate from cells in the uterine lining. 

This doesn't mean adenomyosis is an inherited genetic disease or that having a KRAS mutation means someone will develop cancer. These are acquired changes found within particular cells and are being studied as clues to how adenomyosis develops.

Cell Transformation a.k.a. Metaplasia

Not every case fits neatly with the idea of tissue growing inward from the uterine lining.

Another proposed explanation is metaplasia, meaning certain cells already located within the uterine muscle change into endometrial-like cells. Researchers have looked at Müllerian remnants, which are cells left from reproductive tract development before birth, as well as adult stem or progenitor cells as possible sources. 

Researchers haven't established that this is what happens in every case. It may help explain why adenomyosis can appear in different locations and patterns within the uterus.

Hormonal Fuel 

Adenomyosis is considered an estrogen-responsive condition. Research has identified altered estrogen activity within adenomyosis tissue, along with changes in progesterone signaling. These hormonal features may help adenomyosis lesions survive, grow, and contribute to inflammation. 

This becomes especially relevant during perimenopause.

Estrogen doesn't simply decline in a straight line during the menopause transition. Dr. Tang explains that levels can fluctuate significantly, and ovulation becomes less consistent. That means progesterone exposure also varies from one cycle to another.

Those hormonal shifts may help explain why bleeding and pain can become unpredictable in a woman who has adenomyosis during perimenopause. They also help explain why Dr. Tang pays close attention to bleeding in women with adenomyosis who begin estrogen as part of Menopause Hormone Therapy (MHT).

Hormones appear to influence the activity of adenomyosis. That is different from saying that normal estrogen levels are the sole cause of the condition.

Inflammation Cycle

Researchers are also studying inflammation as part of adenomyosis.

Adenomyosis tissue shows changes involving inflammatory signaling, blood-vessel growth, nerve growth, and uterine muscle function. These processes may contribute to symptoms including painful periods and heavy menstrual bleeding. 

More recent research suggests that the disease may involve a cycle in which tissue disruption, hormonal signaling, immune activity, and fibrosis, or the formation of fibrous tissue, reinforce one another. 

This does not mean adenomyosis is simply an “inflammation problem” that can be solved by reducing inflammation through food or supplements. The biology is more complicated, and inflammation appears to be one part of the disease process.

Who is more likely to develop adenomyosis?

Adenomyosis is most frequently diagnosed in women aged 40 to 50 who are navigating perimenopause and in women who have given birth. Previous procedures involving the uterus, including C-section and other uterine surgeries, have also been associated with adenomyosis in some studies.

Diagnosis is changing. Better ultrasound and MRI techniques mean clinicians can identify adenomyosis without waiting until a hysterectomy provides uterine tissue for examination. That has helped make it clear that adenomyosis can also affect younger women.

The bigger message is that there probably isn't one adenomyosis story.

A woman can develop adenomyosis without having had a C-section or other uterine surgery. Having children doesn't mean a woman will develop it. Genetics, hormones, inflammation, uterine injury, and the biology of the cells within the uterus are all being investigated as possible contributors.

A history of C-section, D&C, or fibroid surgery doesn't diagnose adenomyosis. When it appears alongside increasingly heavy periods, worsening pain, bloating, or pelvic pressure, though, it is useful information to share with a gynecologist.

Can adenomyosis cause weight gain or an “adenomyosis belly”?

Not necessarily. Adenomyosis can cause bloating, pelvic pressure, and enlargement of the uterus, which may make the abdomen feel or appear fuller.

On imaging, the uterus may appear enlarged, swollen, or more rounded. That distinction matters: Abdominal bloating or pelvic fullness isn't necessarily the same as gaining body fat or body weight.

Can you take menopause hormone therapy if you have adenomyosis?

Having adenomyosis does not automatically exclude a woman from using Menopause Hormone Therapy (MHT). But, your treatment may need to be adjusted if estrogen contributes to increased bleeding or pain.

This is an especially important issue for women whose adenomyosis hasn't previously been diagnosed. Dr. Tang explains that a woman may start estrogen and then notice that her periods become heavier, last longer, or occur between expected periods. An underlying condition like adenomyosis may be contributing.

That doesn't necessarily mean estrogen needs to be abandoned.

Your dose of Progesterone or progestin may need particular attention, according to Dr. Tang. Micronized progesterone may not provide enough suppression for some women with significant adenomyosis or endometriosis symptoms. Depending on the woman's needs, a clinician may consider a stronger progestin or a progesterone-containing IUD to help manage bleeding.

Unscheduled bleeding after starting or changing MHT shouldn't automatically be attributed to the hormones themselves. The timing of bleeding, the MHT regimen, the adequacy of progestogen protection, and possible uterine causes all need to be considered.

Adenomyosis may be part of that picture.

“Treatment should follow a complete individualized assessment,” Dr. Haver says.

Women with adenomyosis who are considering MHT, or who develop significant changes in bleeding after starting it, should discuss those symptoms with a clinician familiar with menopause and gynecologic conditions.

What happens to adenomyosis after menopause?

Adenomyosis is estrogen-responsive, and symptoms often become less active as ovarian estrogen levels fall after menopause. The course can vary, which is particularly relevant for women using MHT.

Bleeding after menopause should not simply be assumed to be adenomyosis. New bleeding requires evaluation to identify the cause, particularly when it begins after starting or changing MHT. As Dr. Haver emphasizes, the timing, hormone regimen, progestogen protection, and possible uterine causes all matter.

When should you talk to a gynecologist about adenomyosis symptoms?

Talk with a gynecologist when bleeding, pain, or pelvic symptoms become significantly different from your usual pattern or begin interfering with daily life.

Dr. Tang specifically points to sudden changes in the amount of bleeding, increasing menstrual pain, and unpredictable bowel or pelvic symptoms as reasons to seek evaluation. A pelvic ultrasound may help identify adenomyosis, fibroids, or another condition.

Getting answers can take far too long. Women with endometriosis or adenomyosis can experience symptoms for an average of seven years before receiving a final diagnosis, says Dr. Tang. 

That delay matters. Heavy bleeding and pelvic pain may be common, but that doesn't mean women should be expected to organize their lives around them.

“Heavy bleeding is not something you should be expected to endure,” Dr. Haver says. “You deserve answers and treatment options.”

If symptoms are changing, particularly after a uterine procedure or during the menopause transition, Dr. Haver recommends asking more specific questions:

• Could adenomyosis be contributing?

• What needs to be ruled out?

• What evaluation is appropriate?

• What are my treatment options?

• How could this affect my menopause treatment plan?

As Dr. Tang puts:  “Common does not mean normal.”