Besides cancer, why would the uterus lining be thick after menopause?

Overgrowth or polyp: Women often experience an overgrowth of the lining of their uterus, the endometrium, called hyperplasia. The hyperplasia may be only simple, requiring only hormonal treatment, or complex, with atypia, which is more worrisome since it can be precancerous, best treated with hysterectomy. If the uterine lining's thickness was noted on an ultrasound, it may also be due to a polyp, usually benign.