Theories About What Causes Endo — and What We Still Don’t Know
Despite affecting approximately 1 in 10 women and people assigned female at birth, the exact cause of endometriosis remains one of medicine’s enduring mysteries. While researchers have proposed several theories over the years, none fully explain why endometriosis develops in some people and not others. Understanding these theories is an important step toward better care, earlier diagnosis, and ultimately — finding a cure.
Main Theories Explored by Scientists
1. Retrograde Menstruation
This is the most widely accepted theory. It suggests that during menstruation, some menstrual blood flows backward through the fallopian tubes into the pelvic cavity instead of leaving the body. This tissue then implants and grows outside the uterus.
However, retrograde menstruation occurs in many people who do not develop endometriosis, so it likely isn’t the whole explanation.
Reference: Mayo Clinic (2024)
2. Genetic and Hereditary Factors
Studies show that endometriosis tends to run in families. If your mother or sister has endo, your risk may be higher, suggesting a possible genetic component. However, no specific “endo gene” has yet been identified.
Reference: Endometriosis UK (2023)
3. Immune System Dysfunction
Some experts believe the immune system in people with endometriosis fails to recognise and destroy endometrial-like cells growing outside the uterus. This could explain the inflammation and autoimmune-like symptoms reported by many patients.
Reference: National Institute of Health (NIH), 2023
4. Coelomic Metaplasia
This theory proposes that cells lining the pelvic cavity can transform into endometrial-like cells under certain conditions. It may explain cases where endometriosis occurs in individuals without menstruation (e.g., rare cases in men or prepubescent girls).
Reference: British Society for Gynaecological Endoscopy (BSGE), 2022
5. Stem Cell Theory
Some researchers suggest that bone marrow or other stem cells may differentiate into endometrial-like tissue in various parts of the body, potentially explaining deep infiltrating or distant endometriosis (such as in the lungs or brain).
Reference: Journal of Endometriosis and Pelvic Pain Disorders, 2021
What We Still Don’t Know
No single cause has been universally accepted. It’s likely that endometriosis develops from a combination of genetic, hormonal, immunological, and environmental factors. Key questions remain:
- Why does endometriosis behave so differently between individuals?
- What determines mild versus severe disease?
- Can endometriosis be prevented?
Until clearer answers are found, raising awareness and investing in research remain essential.
🔍 Understanding possible causes helps us better advocate for ourselves and others. Science may not have all the answers yet, but every study brings us closer.
References
- Mayo Clinic. (2024). Endometriosis Causes. Available at: https://www.mayoclinic.org/diseases-conditions/endometriosis/symptoms-causes/syc-20354656 [Accessed 7 Aug. 2025].
- Endometriosis UK. (2023). Genetics and Endometriosis. Available at: https://www.endometriosis-uk.org/genetics [Accessed 7 Aug. 2025].
- National Institute of Health (NIH). (2023). Immune Dysfunction in Endometriosis. Available at: https://www.nih.gov [Accessed 7 Aug. 2025].
- British Society for Gynaecological Endoscopy (BSGE). (2022). Endometriosis Facts. Available at: https://www.bsge.org.uk [Accessed 7 Aug. 2025].
- Journal of Endometriosis and Pelvic Pain Disorders. (2021). Stem Cell Theory in Endometriosis. Available at: https://journals.sagepub.com [Accessed 7 Aug. 2025].
