Short answer · Medically reviewed summary · Last updated: 2026-04-07
Adenomyosis is a gynecological condition in which endometrial-like tissue, which normally lines the uterus, grows into the muscular wall of the uterus, leading to thickening, inflammation, and often significant pain. When this tissue invades the muscular wall (the myometrium), it continues to act as it would during a normal menstrual cycle—thickening, breaking down, and bleeding—but because it is trapped within the muscle, it causes the uterus to enlarge and become tender. This condition primarily affects the reproductive system, specifically the uterus, but the resulting chronic inflammation and pelvic pain can significantly impact a patient’s overall quality of life. Classifications and Prevalence Adenomyosis is generally classified into two forms: diffuse, where the abnormal tissue is spread throughout the uterine wall, and focal (sometimes called an adenomyoma), where the tissue forms a concentrated mass or nodule.
What is Adenomyosis
What is Adenomyosis? Plain-language, medically reviewed definition plus the lived reality told by patients.
Adenomyosis is a gynecological condition in which endometrial-like tissue, which normally lines the uterus, grows into the muscular wall of the uterus, leading to thickening, inflammation, and often significant pain.
When this tissue invades the muscular wall (the myometrium), it continues to act as it would during a normal menstrual cycle—thickening, breaking down, and bleeding—but because it is trapped within the muscle, it causes the uterus to enlarge and become tender. This condition primarily affects the reproductive system, specifically the uterus, but the resulting chronic inflammation and pelvic pain can significantly impact a patient’s overall quality of life.
Classifications and Prevalence
Adenomyosis is generally classified into two forms: diffuse, where the abnormal tissue is spread throughout the uterine wall, and focal (sometimes called an adenomyoma), where the tissue forms a concentrated mass or nodule. While historically considered rare due to the difficulty of diagnosis, modern imaging techniques suggest it is quite common, with prevalence estimates varying widely from 5% to 70% in the general population, depending on the diagnostic criteria used.
Who is Affected?
Adenomyosis is most frequently diagnosed in women between the ages of 35 and 50, particularly those who have previously given birth or undergone uterine surgeries, such as a Cesarean section. While it is often compared to endometriosis, these are distinct conditions; endometriosis involves tissue growing outside the uterus, whereas in Adenomyosis, the tissue is embedded within the uterine wall. Unlike endometriosis, which is often associated with infertility, Adenomyosis has a unique clinical presentation characterized by heavy, prolonged menstrual bleeding (menorrhagia) and severe menstrual cramps (dysmenorrhea).
Understanding the Mechanism
The exact cause of Adenomyosis remains a subject of ongoing research, though it is widely believed that the integrity of the boundary between the endometrium and the myometrium is compromised, allowing cells to migrate into the muscle. This process is thought to be driven by a combination of hormonal factors—particularly high estrogen levels—and potential trauma to the uterine lining.
Medical Disclaimer: This information is provided for educational purposes only and does not constitute medical advice, diagnosis, or treatment. Always seek the advice of a physician or other qualified health provider with any questions regarding a medical condition.
References
- NIH Genetic and Rare Diseases Information Center (GARD)
- Orphanet: The portal for rare diseases and orphan drugs
- American College of Obstetricians and Gynecologists (ACOG)
