Short answer: no one really knows. Long answer: there are numerous theories as to why and when endometriosis develops although none of them have been proven conclusively. Some have big fancy names like retrograde menstruation (menstrual blood refluxing back into the body), metaplasia (residual embryonic cells that respond to hormones), or apoptosis suppression and alteration of endometrial cell fate. Or some go back to genetics, stem calls, immune dysfunction, or oxidative stress and inflammation. Endometriosis lesions can be found in embryos, thus highlighting that it can be laid down before birth. Studies do show there is a genetic component, with increased risks among those with relatives with endometriosis (for example in one study there was an 5.2 increased risk between sisters and 1.6 increased risk in cousins). The oldest theory of what causes endometriosis is that menstrual blood backflows into the pelvis and once there attaches and grows. However, this retrograde menstruation occurs in most individuals with a uterus, but only around 10% develop endometriosis. In addition, endometriotic lesions have distinct characteristics from that of regular endometrial tissue from the uterus.
It matters how we get it, because some treatments are based on not only
how endometriosis behaves and what relieves symptoms but also how it originates.
While endometriosis’ origins continue to be an enigma, studies continue to
highlight new information that can guide care in the future (see some studies below).
References
Crispi, S., Piccolo, M.
T., D'avino, A., Donizetti, A., Viceconte, R., Spyrou, M., ... & Signorile,
P. G. (2013). Transcriptional profiling of endometriosis tissues identifies
genes related to organogenesis defects. Journal of cellular physiology, 228(9), 1927-1934. https://doi.org/10.1002/jcp.24358
Sourial, S., Tempest,
N., & Hapangama, D. K. (2014). Theories on the pathogenesis of
endometriosis. International journal
of reproductive medicine, 2014.
https://doi.org/10.1155/2014/179515
Rahmioglu et al. (2015.
Genetics of Endometriosis. Woman’s Health. https://journals.sagepub.com/doi/pdf/10.2217/whe.15.41
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Theories on endometriosis from before birth:
●
Crispi, S., Piccolo, M. T., D'avino, A., Donizetti, A.,
Viceconte, R., Spyrou, M., ... & Signorile, P. G. (2013). Transcriptional
profiling of endometriosis tissues identifies genes related to organogenesis
defects. Journal of cellular
physiology, 228(9),
1927-1934. https://doi.org/10.1002/jcp.24358
●
Laganà, A. S., Vitale, S. G., Salmeri, F. M., Triolo, O.,
Frangež, H. B., Vrtačnik-Bokal, E., ... & Sofo, V. (2017). Unus pro
omnibus, omnes pro uno: a novel, evidence-based, unifying theory for the
pathogenesis of endometriosis. Medical
hypotheses, 103, 10-20. https://doi.org/10.1016/j.mehy.2017.03.032
●
Signorile, P. G., Baldi, F., Bussani, R., Viceconte, R.,
Bulzomi, P., D'Armiento, M., ... & Baldi, A. (2012). Embryologic origin of
endometriosis: analysis of 101 human female fetuses. Journal of Cellular Physiology, 227(4), 1653-1656. https://doi.org/10.1002/jcp.22888
●
Schuster, M., &
Mackeen, D. A. (2015). Fetal endometriosis: a case report. Fertility and sterility, 103(1),
160-162. Retrieved from https://www.sciencedirect.com/science/article/abs/pii/S0015028214022274
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“… among sisters
there was a 5.2-fold increase in the risk of being diagnosed with
endometriosis”
European Society For
Human Reproduction And Embryology. "Genetic Link To Endometriosis – Unique
Icelandic Study Provides Further Proof." ScienceDaily. ScienceDaily, 5
March 2002. www.sciencedaily.com/releases/2002/02/020228073008.htm
●
“…primary difference was the finding that women who had
relatives with endometriosis had more severe disease, defined as stages III to
IV.”
Dun, E. C., Taylor, R.
N., & Wieser, F. (2010). Advances in the genetics of endometriosis. Genome
medicine, 2(10), 75. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2988445/#!po=0.609756
●
“Endometriosis was
found in 8/136 (5.9%) first-degree relatives of patients and in 4/134 (3.0%)
first-degree relatives of controls in the real-case analysis”
Nouri, K., Ott, J.,
Krupitz, B., Huber, J. C., & Wenzl, R. (2010). Family incidence of
endometriosis in first-, second-, and third-degree relatives: case-control
study. Reproductive Biology and
Endocrinology, 8(1), 85. https://pubmed.ncbi.nlm.nih.gov/20618992/
●
"...the study
identified 19 genetic variants associated with endometriosis, and many of those
variants are also associated with other serious health conditions such as
ovarian cancer, cardiovascular disease and high cholesterol....In this case the
study found several variants in genes involved in sex hormone metabolism,
specifically the genes GREB1, FN1, KDR, CCDC170, ESR1, SYNE1, and FSHB." https://blog.23andme.com/23andme-research/endometriosis/
