Estrogen Replacement Therapy (ERT) is therapy to replace estrogen no longer made by a woman's body because she is post-menopausal or her ovaries have been damaged or removed.

For many women, the amount of estrogen produced by the ovaries decreases around the ages of 45 and 50. This decline, which is not noticed by most women, goes on for several years. As women become older, the decline in estrogen levels becomes greater. This drop eventually causes the menstrual period to become less frequent...