Endometrial thickening is associated with obesity, long-term use of high-dose estrogen in women who have not had hysterectomies, irregular menstrual periods, and the use of medications that act like estrogen. Although endometrial thickening is not cancer, it sometimes leads to uterine cancer, notes the American Congress of Obstetricians and Gynecologists.
The lining of the uterus is called the endometrium. During the menstrual cycle, this lining thickens to prepare the uterus for pregnancy. If a woman does not become pregnant, she sheds the endometrial lining during her menstrual period, explains the ACOG. Some women develop endometrial hyperplasia, a condition characterized by an endometrial lining that is too thick.
Endometrial thickening typically occurs when there is too much estrogen and no progesterone. These hormones play an important role in preparing the uterus for pregnancy and triggering the shedding of the endometrial lining during menstruation. If there is no progesterone, the uterus does not shed the endometrial lining, reports the ACOG. Abnormal uterine bleeding is the most common sign of endometrial thickening, but this condition also causes bleeding after menopause, menstrual cycles lasting fewer than 21 days, and heavier bleeding than usual during menstruation. Women who use estrogen supplements after menopause may need to take progesterone to prevent endometrial thickening.