What Does It Mean When the Endometrium Is Thick?

Hyperplasia, or thickening, of the endometrium, is most often caused by an excess of estrogen without progesterone, according to the American Congress of Obstetricians and Gynecologists, or ACOG. This condition usually occurs after menopause when ovulation ceases or during perimenopause when ovulation is irregular. In either scenario, since ovulation does not occur, progesterone is not made, and the endometrium may continue to grow instead of shed its lining.