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What causes endometriosis?

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The exact cause of endometriosis is not known, but researchers have some theories.

It may result from something called "retrograde menstrual flow," in which some of the tissue that a woman sheds during her period flows through her fallopian tubes into her pelvis. While most women have some retrograde menstrual flow during their periods, not all of these women have endometriosis. Researchers are trying to uncover what other factors might cause the tissue to attach and grow in some women, but not in others.1,2

Researchers believe that endometriosis likely results from a combination of factors, including (but not limited to) some of the following:

  • Because endometriosis runs in families, genes are probably involved with endometriosis to some degree.
  • Estrogen (a hormone involved in the female reproductive cycle) also likely contributes to endometriosis, because endometriosis is an estrogen-dependent, inflammatory disease.
  • In endometriosis, the endometrium may not respond as it should to progesterone, another hormone involved in the female reproductive cycle. This means that the endometrium has "progesterone resistance."
  • In some cases of endometriosis, the immune system fails to destroy endometrial tissue, which enables it to grow outside the uterus. This means immune system dysfunction plays a role in these cases.
  • Environmental exposures in the womb, such as to chemicals like dioxin, have also been linked to developing endometriosis.1

  1. Giudice, L. C. (2010). Endometriosis. New England Journal of Medicine, 362, 2389-2398.[top]
  2. National Library of Medicine, Medline Plus. (2011). Endometriosis. Retrieved December 26, 2011, from [top]

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