It is a gynecological disorder characterized by the presence of endometrial tissue beyond the uterus, most commonly in the ovaries, fallopian tubes and the tissue lining the pelvis, and less frequently beyond the pelvic organs. It is estimated to occur in 10% of women of reproductive age and leads to fertility problems, although effective treatments are available.

There are several theories. One suggests that fragments of the endometrium itself that are shed during menstruation travel from the fallopian tubes to the ovaries and eventually enter the abdominal cavity. It has also been postulated that endometrial cells may travel through the bloodstream or lymphatic vessels to another location, or that cells located outside the uterus may transform into endometrial cells. Additionally, an alteration of the immune system has been suggested in which the immune system is not able to destroy the ectopic tissue deposited outside the uterus. However, the exact cause of endometriosis remains unclear.

In addition, apart from the hereditary-familial component described for endometriosis, there are other factors that increase the risk of presenting this condition, such as the following:

  • Not having given birth.
  • Starting the period at an early age, or reaching menopause at an advanced age, which implies a greater exposure to estrogens.
  • Irregular menstrual cycles, either short (less than 27 days), or heavy menstrual cycles of more than seven days.
  • Low body mass index.
  • Disorders of the reproductive system or structural abnormalities of the uterus.

Its etiology is complex, environmental, hereditary and hormone-dependent. In this sense, a variable heritability of 26-50% has been determined. Due to its potential impact on health care and the lack of knowledge of the molecular triggering mechanisms, a meta-analysis has been carried out on 11 data sets currently available, which has allowed the study of a total of up to 17,000 cases of endometriosis and almost 200,000 controls. This has allowed the identification of up to 13 risk loci in genes that are part of the signaling pathways and functionality of sex steroid hormones in women, confirming their involvement in the development of this condition.


Since it is endometrial tissue follows the same cycle as the corresponding tissue located in the uterus with menstruation in response to hormones, so it may bleed, but will be confined in the space of the pelvis causing pain and inflammation. It is a pain similar to that of menstrual periods, but of greater intensity that may also increase over time. The intensity of endometriosis symptoms does not depend on the amount of endometrial tissue outside its usual place. Symptoms are highly variable among women, but the most common include:

  • Painful periods (dysmenorrhea). Pain and cramping may begin before and continue for several days after the period. It may extend to the lower back and abdomen.
  • Irregular menses.
  • Pain during or after sexual intercourse.
  • Pain during bowel movements or urination most likely during the menstrual period.
  • Excessive bleeding including intermenstrual bleeding.

Other symptoms that may accompany endometriosis especially during the period will depend on the location of the endometrial tissue, abdominal swelling, diarrhea or diarrhea.Other symptoms that may accompany endometriosis especially during the period will depend on the location of the endometrial tissue, abdominal swelling, diarrhea or constipation, rectal bleeding (large bowel involvement), frequent and urgent need to urinate, bloody urine (bladder involvement). Being estrogen dependent, symptoms improve after menopause and during pregnancy.


It is not possible to establish guidelines for the prevention of endometriosis since its cause is unknown. It is a common disease that probably begins to develop with the onset of menstruation, although it is not diagnosed until the age of 25-35 years generally. However, it is possible to reduce estrogen exposure as much as possible by following a healthy diet based on foods rich in fiber, iron and omega-3, avoiding alcohol and caffeinated beverages, as well as leading an active life and exercising regularly.

Number of observed variants

13.5 million variants

Number of risk loci analyzed in the study

13 loci


Smolarz B et al. Endometriosis: Epidemiology, Classification, Pathogenesis, Treatment and Genetics (Review of Literature). Int J Mol Sci. 2021;22(19):10554.

MSD Manuals. Endometriosis [March 2022]

MedlinePlus. Endometriosis [March 2022]

Sapkota Y et al. Meta-analysis identifies five novel loci associated with endometriosis highlighting key genes involved in hormone metabolism. Nat Commun. 2017;8:15539.

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