The endometrium is the type of tissue that lines the inside of the uterus. In endometriosis, tissue similar to the endometrium grows outside the uterus. Endometriosis can be a painful condition, especially during menstruation, and endometriosis can impair fertility. Research into the patient experience of this condition has suggested that we redefine endometriosis as a syndrome that includes both these ectopic uterine tissue deposits and the symptoms they cause, since some people with ectopic endometrial tissue don’t experience any symptoms.[1]
What is endometriosis?
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•Last Updated: May 16, 2025
Endometriosis is a condition in which tissue similar to the endometrium grows outside the uterus, leading to pain, particularly during menstruation, and potential fertility issues. Research suggests that it may be more accurately defined as a syndrome that encompasses both the ectopic tissue and the symptoms experienced because some individuals may have the tissue without any symptoms.