In the past, hormone therapy (HT) was widely recommended for the treatment of menopause and menopausal symptoms as well as in the prevention of osteoporosis and heart disease. A large study known as the Women's Health Initiative (WHI) shed new light on how HT is viewed.

What Is Hormone Therapy?

Hormone therapy is a treatment that is used to supplement the body with either estrogen alone or estrogen and progesterone in combination. Estrogen and progesterone are hormones that are produced by a woman's ovaries. When the ovaries no longer produce adequate amounts of these hormones (as in menopause), HT can be given to supplement the body with adequate levels of estrogen and progesterone.

Why Does the Body Need Estrogen and Progesterone?

Estrogen and progesterone together thicken the lining of the uterus, preparing it for the possible implantation of a fertilized egg. Estrogen also influences how the body uses calcium, an important mineral in the building of bones, and helps maintain healthy levels of cholesterol in the blood. Estrogen also keeps the vagina healthy.

As menopause nears, the ovaries reduce most of their production of these hormones. Lowered or fluctuating estrogen levels may cause menopause symptoms such as hot flashes, and medical conditions such as osteoporosis. Hormone therapy helps to replenish the estrogen, relieving some of the symptoms of menopause and helping to prevent osteoporosis.

Why Is Progesterone Taken?

Progesterone is used along with estrogen in women who still have their uterus. In these women, if taken without progesterone, estrogen increases a woman's risk for cancer of the endometrium (the lining of the uterus). During a woman's reproductive years, endometrial cells are shed during menstruation. When the endometrium is no longer shed, estrogen can cause an overgrowth of cells in the uterus, a condition that can lead to cancer.

Progesterone reduces the risk of endometrial cancer by making the endometrium shed each month. As a result, women who take progesterone may have monthly bleeding. Monthly bleeding can be lessened and, in some cases, eliminated by taking progesterone and estrogen together continuously. Women who have had a hysterectomy (removal of the uterus through surgery) usually do not need to take progesterone.

What Are the Types of Hormone Therapy?

There are two main types of hormone therapy:

Estrogen Therapy: Estrogen is taken alone. Doctors most often prescribe a low dose of estrogen to be taken as a pill or patch every day. Estrogen may also be prescribed as a cream. You should take the lowest dose of estrogen needed to relieve menopause symptoms and/or to prevent osteoporosis.
Progesterone/Progestin-Estrogen Hormone Therapy: Also called combination therapy, this form of HT combines doses of estrogen and progesterone (progestin is a synthetic form of progesterone). Estrogen and a lower dose of progesterone also may be given continuously to prevent the regular, monthly bleeding can occur when combination HT is used. The current recommendation is to take the lowest dose of hormone therapy for the shortest time consistent with the reason the woman is taking the therapy. Like all prescription medications, HT should be re-evaluated each year.