Menopausal Hormone Therapy and Cancer – National Cancer Institute

What is menopausal hormone therapy?

Menopausal hormone therapy (MHT) is a treatment that doctors may recommend to relieve common symptoms of menopause and to address long-term biological changes, such as bone loss, that result from declining levels of the natural hormones estrogen and progesterone in a womans body during and after the completion of menopause. (More information is available on the MedlinePlus Menopause page.)

MHT usually involves treatment with estrogen alone, estrogen plus progesterone, or estrogen plus progestin, which is a synthetic hormone with effects similar to those of progesterone. Women who have had a hysterectomy are generally prescribed estrogen alone. Women who have not had this surgery are prescribed estrogen plus progestin, because estrogen alone is associated with an increased risk of endometrial cancer, whereas research has suggested that estrogen plus progestin may not be.

How do the hormones used in MHT differ from the hormones produced by a womans body?

The hormones used in MHT come from a variety of plants and animals, or they can be made in a laboratory. The chemical structure of these hormones is similar, although usually not identical, to those of hormones produced by womens bodies.

The U.S. Food and Drug Administration (FDA) has approved many hormone products for use in MHT. FDA-approved products have undergone extensive testing and are produced under standardized conditions to ensure that every dosewhether in a pill, a skin patch, or a creamcontains the proper amount of the appropriate hormones. These FDA-approved products are available only with a doctors prescription. The FDA has more information about MHT in MenopauseMedicines to Help You.

Non-FDA-approved hormone products, sometimes referred to as bio-identical hormones, are widely promoted and sold without a prescription on the Internet. Claims that these products are safer or more natural than FDA-approved hormonal products are not supported by credible scientific evidence. The FDA provides more information about these products in Menopausal Hormone Therapy and Bio-identical Hormones.

Where does evidence about risks and benefits of MHT come from?

The most comprehensive evidence about risks and benefits of MHT comes from two randomized clinical trials that were sponsored by the National Institutes of Health as part of the Womens Health Initiative (WHI):

More than 27,000 healthy women who were 50 to 79 years of age at the time of enrollment took part in the two trials. Although both trials were stopped early (in 2002 and 2004, respectively) when it was determined that both types of therapy were associated with specific health risks, longer-term follow-up of the participants continues to provide new information about the health effects of MHT.

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Menopausal Hormone Therapy and Cancer - National Cancer Institute