Estrogen therapy (ET) is a treatment that helps replenish low estrogen levels. This therapy involves taking the hormone estrogen on a regular basis.

The body naturally produces less estrogen after menopause, when the ovaries are removed, or as a result of some other health conditions. ET can help reverse the effects of low estrogen, which may include severe menopausal symptoms, such as hot flashes and insomnia, and long-term problems, such as weak and brittle bones (osteoporosis).

Estrogen therapy is also called unopposed estrogen therapy because a second hormone (progestin) is not used along with the estrogen. Estrogen used alone can cause cancer of the lining of the uterus (endometrial cancer). For this reason, unless you have had your uterus removed, estrogen usually is combined with progestin. This combined therapy is called estrogen and progestin therapy.