Post-menopausal uterus. X-ray of the uterus (white, centre) of a post-menopausal woman, showing degeneration of the inner uterine lining (endometrium, mottled appearance). The pre- menopausal endometrium contains many glands, responsible for the production of mucus during pregnancy. After the menopause, their number and activity decreases, causing the endometrium to shrink or atrophy. The menopause marks the end of the fertile period of a woman's life. It is caused by a cessation in the production of the female sex hormone oestrogen, and usually occurs between the ages of 45 and 55. A contrast medium reveals the position of the uterus on the X-ray.