Two common and commonly confused conditions. Here’s what the science actually says. 

You might have heard these two words before — maybe from a doctor, a parent, or on social media. Endometriosis and adenomyosis are both real medical conditions. They sound similar, they can feel similar, and yet they are quite different. Let’s break them both down clearly — based on science, not In our myth. 

First: A Quick Bit of Biology 

The uterus is a pear-shaped organ found in people assigned female at birth. It has three layers: a thin inner lining, a thick muscle wall called the myometrium, and an outer covering. Every month during a menstrual cycle, the inner lining thickens to prepare for a possible pregnancy. If no pregnancy happens, that lining sheds. And that’s what a period is. 

Both conditions involve tissue growing where it shouldn’t. But here’s an important scientific point: endometriosis is not simply the uterine lining moving around. It is a distinct disease involving tissue that resembles the lining but is not identical to it. That distinction matters. 

What Is Endometriosis? 

Endometriosis (say it: en-doh-mee-tree-OH-sis) is a disease where tissue that behaves similarly to, but not the same as, the uterine lining grows in places it shouldn’t be. 

It is most commonly found on the ovaries, bowel, and bladder. Bladder and bowel endometriosis is actually very common, not rare it is simply under-diagnosed because many specialists don’t look beyond the reproductive organs. Endometriosis has also been found on the diaphragm (the dome-shaped muscle beneath your lungs), the lungs, and in other parts of the body entirely. 

The reach of endometriosis is often underestimated. Specialist curiosity beyond the pelvis is essential and too rare. 

Endometriosis affects people of all genders. While it is most common in people assigned female at birth, it can affect transgender men, non-binary people, and, in documented cases, people assigned male at birth, too. It is not exclusively a ‘women’s condition.’ 

Current research suggests endometriosis affects around 10–15% of people assigned female at birth globally. It can cause: 

• Very painful periods — sometimes severely debilitating 

• Pain during or after sex 

• Bladder problems — pain, urgency, or bleeding when urinating 

• Bowel problems — pain, bloating, or bleeding from the bowel during a period 

• Shoulder or chest pain (when on the diaphragm) 

• Heavy periods and fatigue 

• Difficulty getting pregnant 

Endometriosis is not rare. It affects an estimated 10–15% of people assigned female at birth — yet on average it takes 7–10 years to get a correct diagnosis. 

It is diagnosed through a surgery called a laparoscopy, where a tiny camera is used to look inside the body. A thorough specialist will look beyond the pelvis. There is currently no cure, but hormone therapy, pain management, and specialist surgery can all help. 

What Is Adenomyosis? 

Adenomyosis (say it: ad-en-oh-my-OH-sis) is different. Here, tissue similar to the uterine lining grows into the muscular wall of the uterus itself, not outside it. The uterus often becomes larger and feels soft and swollen (doctors sometimes call this ‘boggy’). 

Common symptoms include: 

• Very heavy periods — sometimes with large blood clots 

• Severe period cramps 

• A bloated or tender lower abdomen 

• Periods that last longer than usual 

• A feeling of heaviness or pressure in the pelvis 

Adenomyosis was once thought to mainly affect people in their 30s and 40s but research now shows it can affect younger people, including teenagers. 

Unlike endometriosis, adenomyosis can often be seen on an ultrasound scan or MRI; no surgery is needed to diagnose it. Treatments range from pain relief and hormonal medicines to surgical options in more severe cases. 

Side by Side: How Are They Different? 

 

	Endometriosis	Adenomyosis
What it is	A disease, tissue similar to (but not the same as) the uterine lining, growing outside the uterus	Uterine-lining-like tissue growing into the uterus muscle wall
Where it grows	Ovaries, bowel, bladder, diaphragm, and beyond	Inside the uterus wall only
Who gets it	Any gender — all people can be affected	Primarily people with a uterus
Main symptoms	Pelvic pain, bowel/bladder pain, fatigue, heavy periods	Very heavy periods, severe cramping, pelvic pressure
Diagnosed by	Surgery (laparoscopy) by a specialist	Ultrasound or MRI scan
Can they overlap?	Yes — around 1 in 5 people have both	Yes — around 1 in 5 people have both

 

Can You Have Both at the Same Time? 

Yes, and it’s more common than many people realise. Research suggests that around 1 in 5 people with endometriosis also have adenomyosis. This is why symptoms can be complex, and why finding a knowledgeable specialist matters so much. 

Why Are These Conditions So Often Missed? 

Both conditions are historically under-researched and under-diagnosed. The average time to an endometriosis diagnosis is 7 to 10 years. Symptoms are frequently dismissed as ‘just bad periods’, particularly in younger people. 

But severe period pain is not normal. Pain that keeps you from going to school or work, or from doing daily activities, is a sign that something needs to be investigated. 

Part of the problem with endometriosis specifically is that many clinicians only look at the reproductive organs, missing disease on the bowel, bladder, diaphragm, and elsewhere. Access to truly specialist, curious, thorough care is still far too limited. 

If you or someone you know experiences very painful or very heavy periods, it is worth speaking to a doctor and asking specifically about both conditions. 

The Bottom Line 

Endometriosis and adenomyosis are both real, scientifically recognised diseases, not myths, not exaggerations. Endometriosis is a whole-body disease that can affect any gender and reach far beyond the pelvis. Adenomyosis lives within the uterus wall and causes its own serious set of symptoms. 

Neither condition is fully understood yet; research is still growing. But one thing is clear: the more we talk about them accurately, the sooner people can get the help they deserve.