A woman’s body makes different hormones throughout her life. The three major sex hormones made by the ovaries are the so-called “female” sex hormones estrogen and progesterone, and the so-called “male” sex hormone testosterone. During reproductive years, these hormones prepare the body for pregnancy, but they also affect other aspects of the body, health and well-being. After natural menopause or when the ovaries are surgically removed, these hormone levels decrease, leading to menopausal symptoms. Testosterone continues to be made by the adrenal glands, although levels decline as women age.
Most hormone replacement therapy (HRT) preparations used to treat menopausal symptoms contain one or both of the female sex hormones. Estrogen replacement therapy (ERT) usually refers to hormone replacement therapy containing estrogen alone. ERT tablets, skin patches, gels, sprays, lotions and a vaginal ring (Femring) are available. Combination estrogen-progesterone preparations are available as tablets and patches. Progesterone-only preparations are available as a pill, injections, vaginal gel, or an intrauterine device (IUD). Testosterone therapy is currently not approved for women, and it is not included in any of the combination therapies available in the United States.
Using estrogen alone increases the risk for uterine cancer. Adding progesterone to hormone replacement protects the uterus from cancer. For this reason, estrogen-only preparations are usually only used in postmenopausal women who have had hysterectomies. Because they have no uterus, these women have no risk of uterine cancer and therefore don’t require progesterone.
Progesterone therapy is usually added to estrogen therapy in women who still have a uterus.