Endo Basics: What is endometriosis?

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Endometriosis has some unique characteristics, and we continue to find out new things about it. Understanding exactly what it is and how it functions can help us make better sense of the symptoms we experience as well as guide our decisions for treatment. Here are some key points to consider:

  • Endometriosis is defined as tissue similar to the lining of the uterus (endometrium) that is found outside of the uterus (Becker, 2015).  This can be in the pelvis and abdominal area, but has been found in areas outside the pelvis (like the diaphragm). This means it affects more than just reproductive organs! (See Locations of Endometriosis)
  • Endometriosis has some key differences from the lining of the uterus in both its structure and function. Endometriotic lesions are capable of high estrogen production and have a resistance to the effects of progesterone (Cristescu, Velişcu, Marinescu, Pătraşcu, Traşcă, & Pop, 2013). Endometriosis can also produce cytokines and prostaglandins and is capable of the growth of new blood vessels and nerves (Hey-Cunningham, Peters, Zevallos, Berbic, Markham, & Fraser, 2013; Reis, Petraglia, & Taylor, 2013; Bulun et al., 2012; Chaban, 2012). (See Role of Estrogen Receptor-β in Endometriosis and Progesterone Resistance in Endometriosis)
  • Endometriosis is an inflammatory disorder that can lead to scarring and adhesions (Becker, 2015; Mao & Anastasi, 2010). (See Inflammation with Endometriosis)
  • The severity of symptoms does not necessarily correlate with extent of lesions (McCance & Huether, 2014). (See What influences pain levels)
  • The location of the lesions and the presence of adhesions can also affect the symptoms experienced (Lu, Zhang, Jiang, Zou, & Li, 2014). (See Locations of Lesions and Where Pain Is Felt)
  • Most symptoms arise from chronic inflammation, noxious chemical release such as prostaglandins, effects on the musculoskeletal system, and/or adhesions (Koga, Yoshino, Hirota, Hirata, Harada, & Osuga, 2014). (See Symptoms)
  • An estimated 30-50% of patients with endometriosis are infertile due to the inflammatory environment and physical abnormalities such as adhesions (Koga, Yoshino, Hirota, Hirata, Harada, & Osuga, 2014). (See Fertility Issues)


Becker, C. (2015). Diagnosis and management of endometriosis. Prescriber26(20), 17-21. 

Bulun, S. E., Monsavais, D., Pavone, M. E., Dyson, M., Xue, Q., Attar, E., … Su, E. J. (2012). Role of Estrogen Receptor-β in Endometriosis. Seminars in Reproductive Medicine30(1), 39–45. http://doi.org/10.1055/s-0031-1299596 

Chaban, V. (2012). Primary afferent nociceptors and visceral pain. INTECH Open Access Publisher. Retrieved from http://www.intechopen.com/books/endometriosis-basicconcepts-and-current-research-trends/primaryafferent-nociceptors-and-visceral-pain  

Cristescu, C., Velişcu, A. N. D. R. E. E. A., Marinescu, B., Pătraşcu, A. N. C. A., Traşcă, E. T., & Pop, O. T. (2013). Endometriosis–clinical approach based on histological findings. Rom J Morphol Embryol54(1), 91-97. 

Hey-Cunningham, A. J., Peters, K. M., Zevallos, H. B., Berbic, M., Markham, R., & Fraser, I. S. (2013). Angiogenesis, lymphangiogenesis and neurogenesis in endometriosis. Front Biosci (Elite Ed)5, 1033-56. 

Koga, K., Yoshino, O., Hirota, Y., Hirata, T., Harada, M., & Osuga, Y. (2014). Infertility Treatment of Endometriosis Patients. In Endometriosis (pp. 431-443). Springer Japan. 

Lu, Z., Zhang, W., Jiang, S., Zou, J., & Li, Y. (2014). Effect of lesion location on endometriotic adhesion and angiogenesis in SCID mice. Archives of gynecology and obstetrics289(4), 823-830. 

Mao, A. J., & Anastasi, J. K. (2010). Diagnosis and management of endometriosis: The role of the advanced practice nurse in primary care. Journal of the American Academy of Nurse Practitioners22(2), 109-116.

McCance, K. L., & Huether, S. E. (2014). Pathophysiology: The Biological Basis for Disease in Adults and Children (7th ed.). St. Louis, MO: Elsevier.

Reis, F. M., Petraglia, F., & Taylor, R. N. (2013). Endometriosis: hormone regulation and clinical consequences of chemotaxis and apoptosis. Human reproduction update19(4), 406-418.