During the reproductive years, a woman’s ovaries produce the hormones estrogen and progesterone. Estrogen works to regulate a woman’s monthly menstrual cycle and secondary sexual characteristics (such as breast development and function), and also rises at different times in the menstrual cycle to prepare the body for fertilization and reproduction. Progesterone also rises in a cyclical fashion to prepare the uterus for possible pregnancy and to prepare the breasts for lactation (milk production). As a woman reaches menopause, typically around 50 years old, her body produces less and less estrogen and progesterone. It is estimated that 40 million women will reach menopause in the next 20 years.
Decreased levels of estrogen during menopause may cause hot flashes, vaginal dryness, sleep disturbances, or other bothersome side effects. The dryness of tissue surrounding the vagina and urethra may cause pain during sexual intercourse or urination, and HRT helps to relieve these and other menopausal symptoms. Hormone replacement therapy (HRT) is synthetic estrogen and progesterone (progestin) designed to “replace” a woman’s depleting hormone levels.
(“Hormone Replacement Therapy”. Imaginis. http://www.imaginis.com)