The lining of the uterus (endometrium) becomes unusually thick because of having too many cells (hyperplasia). It's not cancer, but in certain women, it raises the risk of developing endometrial cancer, a type of uterine cancer.

What is the most common cause of endometrial thickening?

The most common cause of endometrial hyperplasia is having too much estrogen and not enough progesterone. That leads to cell overgrowth. There are several reasons you might have a hormonal imbalance: You've reached menopause.

What causes endometrium to thicken?

2 Estrogen is the hormone that is responsible for causing the normal thickening of the endometrium during the first half of your menstrual cycle. When balanced with the right amount of progesterone, your endometrium builds up, but then thins out not allowing for extra, abnormal growth.