Menopausal women experience a gradual decrease in the production of estrogens, and the proportions they are synthesized in changes. For instance, though estradiol is the primary estrogen produced during a woman’s reproductive years, females that are no longer fertile generate more of the weaker estrogen, estrone, than estradiol. Due to these significant hormonal changes, which may cause hot flashes and a number of other uncomfortable symptoms, many doctors recommend hormone replacement therapy for post-menopausal women. However, this type of therapy is somewhat controversial since a wide range of side effects have been reported with its use, many of which are more serious than the symptoms the treatment is supposed to help remedy.