What Is Hormone Therapy?

Hormones are chemicals produced by glands in the body and are circulated in the blood. Hormone therapy -- also called hormonal therapy, hormone treatment, or endocrine therapy -- is any treatment that adds, blocks, or removes hormones. For certain conditions (such as diabetes or menopause), hormones are given to boost low hormone levels. Sometimes, hormone therapy is used to slow or stop the growth of certain cancers (such as prostate and breast cancer). The female hormones estrogen and progesterone, for example, promote the growth of some breast cancer cells. So hormone therapy may be given to block the body's naturally occurring estrogen and fight the cancer's growth. Sometimes surgery is needed to remove the source of the hormone in question -- in the case of breast cancer, the ovaries may be removed.

When Is It Used?

Hormone therapy is used in women with breast cancer whose tumors are sensitive to the hormones estrogen or progesterone (meaning that hormones cause the cancer to grow). Not all breast cancers are hormone sensitive, so not all breast cancers will respond to a hormone-blocking treatment.

The drugs slow or stop the growth of cancer cells that are present in the body. As an adjuvant (add-on) therapy, hormone therapy helps prevent the original breast cancer from returning and also helps prevent the development of new cancers in the other breast.

Women at an increased risk of developing breast cancer (those with a genetic predisposition or family history) have the option of taking hormone therapy to reduce their chance of ever developing the disease.