Hormone replacement therapy (HRT) is the use of the female hormones estrogen and progesterone to relieve symptoms in women who are either menopausal or have had both ovaries removed. Hormone replacement therapy (HRT) is effective against hot flushes, vaginal dryness, and the mood changes associated with the menopause. It also gives some protection against disease of the heart and blood vessels, and osteoporosis. However, except in people who have undergone hysterectomy, the estrogen component causes a thickening of the lining of the uterus, which may lead to an increased risk of cancer of the endometrium. The progesterone component of the treatment causes a regular shedding of the lining, similar to menstruation, which may lessen this risk.