Like the rest of the body, the ovaries age and the decreased estrogen in the body results in a cessation of the menstrual cycle around the age of 50 (earlier or later, varies by woman), known as menopause. This hormonal change also causes symptoms - hot flashes being the most stereotypical, though many women don't have symptoms. Hormonal replacement therapy (estrogen pills) were used as a way to treat these symptoms, but it was found to have unplanned cardiovascular risks. Similar to hormonal birth control, synthetic and combination therapies were tested to reduce the side effects while keeping options open for women. Prempro is one such treatment (read about the side effects of Prempro).
The discomfort of menopause will subside on its own once the hormones become regulated, usually over the course of a year or two, though the symptoms may recur for up to 5 years. Women with severe symptoms may find relief in treatment.