Hormones are the bodies natural balancers. As we age our bodies produce less of our primary hormone, and this causes diseases, illnesses and other symptoms of aging to develop. Hormone replacement therapy (HRT) is a medical treatment for menopausal, perimenopausal and postmenopausal women. It is also used to lessen the impact of male menopause (andropause) to achieve more desirable lifestyle results. Usually, females receive estrogen and progesterone to supplement their bodies' supply. This reduces the impact of menopause and can improve sex drive. Men receive testosterone to supplement their bodies' supply. This improves sexual function, and muscle retention.