If you've been diagnosed with endometriosis or adenomyosis, or you're trying to understand why your periods are so painful, you've probably come across both terms.
They're often mentioned together, and while they share many symptoms, they are not the same condition.
Understanding the difference is important because although both can cause severe pelvic pain, heavy periods, and fertility challenges, they affect the uterus in different ways and may require different approaches to treatment.
Let's break it down.
What is endometriosis?
Endometriosis is a chronic inflammatory condition in which tissue similar to the lining of the uterus (the endometrium) grows outside the uterus.
These lesions may be found on the:
- Ovaries
- Fallopian tubes
- Pelvic lining (peritoneum)
- Bladder
- Bowel
- Ligaments supporting the uterus
- In rare cases, other areas of the body
Despite often being described as "endometrial tissue growing outside the uterus," experts note that endometriosis lesions are not identical to normal endometrial tissue—they are endometrial-like tissue with distinct biological characteristics.
What is adenomyosis?
Adenomyosis occurs when endometrial tissue grows into the muscular wall of the uterus (the myometrium).
Instead of growing outside the uterus like endometriosis, the tissue is embedded within the uterine muscle, causing the uterus to become enlarged, inflamed, and often very painful.
Think of it this way:
- Endometriosis = outside the uterus
- Adenomyosis = inside the muscle of the uterus
Are endometriosis and adenomyosis the same condition?
No.
Although they share many symptoms, they affect different tissues and are considered distinct gynecologic conditions.
However, they frequently occur together. Studies suggest that a substantial proportion of people with endometriosis also have adenomyosis, although estimates vary depending on how each condition is diagnosed.
What symptoms do they have in common?
Both conditions may cause:
- Severe menstrual cramps
- Chronic pelvic pain
- Pain during sex
- Lower back pain
- Pain with bowel movements
- Fatigue
- Infertility or difficulty becoming pregnant
- Pain that interferes with work, school, or daily activities
Neither condition should be dismissed as "just bad periods."
How are the symptoms different?
Endometriosis is more commonly associated with:
- Pain before and during periods
- Pain with bowel movements
- Pain with urination (if the bladder is involved)
- Gastrointestinal symptoms
- Painful intercourse
- Infertility
Adenomyosis is more commonly associated with:
- Heavy menstrual bleeding
- Passing large blood clots
- A feeling of pelvic pressure
- A tender or enlarged uterus
- Painful, prolonged periods
That said, there is significant overlap, which is why diagnosis can be challenging.
What causes endometriosis and adenomyosis?
Researchers still don't know exactly what causes either condition.
Current evidence suggests they likely result from a combination of:
- Genetics
- Hormonal influences
- Immune system dysfunction
- Inflammation
- Environmental factors
Multiple theories exist, including retrograde menstruation for endometriosis—but no single theory explains every case.
How are they diagnosed?
Endometriosis
Historically, laparoscopic surgery has been considered the gold standard for confirming endometriosis. Today, advances in imaging and clinical evaluation allow many people to begin treatment based on symptoms and imaging findings without immediate surgery, although surgery may still be needed in some cases.
Adenomyosis
Unlike endometriosis, adenomyosis is often identified using:
- Transvaginal ultrasound
- MRI
These imaging techniques have improved significantly and can often detect characteristic changes in the uterine muscle.
Can you have both?
Yes.
Many people diagnosed with endometriosis also have adenomyosis.
Having one condition does not cause the other, but they frequently coexist.
Can they affect fertility?
They can.
Endometriosis has been strongly associated with infertility, although many people with endometriosis conceive naturally.
Adenomyosis may also affect fertility by altering the uterine environment and implantation, though research is still evolving.
A diagnosis does not automatically mean you cannot become pregnant.
How are they treated?
Treatment depends on:
- Your symptoms
- Age
- Whether you're trying to conceive
- Disease severity
- Personal preferences
Options may include:
- NSAIDs for pain relief
- Hormonal therapies
- Pelvic floor physical therapy
- Laparoscopic surgery (for endometriosis)
- Lifestyle strategies to support symptom management
- Hysterectomy in select cases of severe adenomyosis when childbearing is complete
Treatment should always be individualized in partnership with a gynecologist.
When should you see a healthcare provider?
Painful periods are common.
Debilitating periods are not.
If your menstrual pain causes you to:
- Miss work or school
- Cancel plans every month
- Vomit or faint
- Need frequent pain medication
- Experience pain during sex
- Have heavy bleeding that soaks through pads or tampons quickly
it's worth speaking with a healthcare provider, preferably one experienced in diagnosing pelvic pain disorders.
The Bottom Line
Although endometriosis and adenomyosis share many symptoms, they are not the same condition.
Endometriosis occurs outside the uterus, while adenomyosis develops within the muscular wall of the uterus. Both are chronic conditions that can significantly affect quality of life, and both deserve timely diagnosis, compassionate care, and individualized treatment.
Perhaps the most important takeaway is this: severe period pain should never be normalized simply because it's common. If your symptoms are interfering with your life, you deserve to be heard—and you deserve answers.