What is endometriosis?

Endometriosis is characterized by the abnormal growth of tissue that resembles the endometrium, the lining of the uterus, outside the uterus itself. This can occur on the ovaries, fallopian tubes, and other areas within the pelvic cavity. The presence of this endometrial-like tissue can cause pain, irregular bleeding, and potentially fertility issues. Understanding this condition is essential because it highlights the importance of recognizing that the tissue growth occurs outside of its normal location, which distinguishes endometriosis from other conditions related to the endometrium.

The other choices describe different conditions or processes related to the endometrium but do not define endometriosis. Thickening of the endometrium refers to a different phenomenon that can occur due to hormonal imbalances or other factors. The sloughing of the endometrium during menses is a normal part of the menstrual cycle, indicating the shedding of the uterine lining, and is not associated with the disorder in question. Cancer of the uterine lining pertains to endometrial cancer, which is distinctly different as it involves malignancy rather than abnormal tissue growth outside the uterus.