what layer of the uterus is shed during menstruation
In reviewing the causes of endometriosis, it is important to first understand the regular menstrual cycle and how hormones in the body affect the menstrual cycle and the uterus itself. 1  The endometrium is the inner layer of uterine tissue that is shed during menstruation. The thickness of the endometrial layer is related to the egg-producing (ovulatory) cycle and the hormonal levels that regulate this cycle. 2  The endometrium is at its thinnest immediately following menstruation and thickens during the first two weeks of the menstrual cyle.