Hormone therapy

Specialized treatments can stop hormone-responsive tumors in their tracks.

Your endocrine system is a network of small glands that controls growth and metabolism. It also creates natural substances called hormones — chemicals that circulate through your bloodstream to control biological functions throughout the body. But certain cancers — including some breast, ovarian, and prostate cancers — depend on specific hormones to grow. Therapies that stop the supply of these hormones can slow down, and sometimes stop, the reproduction of cancerous cells.

To determine whether hormone therapy will be an effective treatment, your doctor tests the tumor’s cancer cells to see if they have hormone receptors. These receptors, which are present in some but not all cancer cells, are molecules that allow a specific hormone — such as estrogen, progesterone, or testosterone — to attach to the cells and stimulate their growth. If the cells are hormone-responsive, restricting the flow of the specific hormone may stop the cancer from growing.

Approaches to hormone therapy

Doctors have established several techniques for slowing down the hormones that fuel cancer growth, including:

Blocking hormone receptors. Hormones must bind to the receptors in order to stimulate activity in the cell. With this form of treatment, doctors obstruct the receptors using other compounds. The hormones cannot activate growth when their "parking spot" is occupied.
Shutting down hormone production. Certain medications may stop the body from producing hormones. Or, doctors may surgically remove hormone-producing organs, such as the ovaries or testicles.
Eradicating or altering hormone receptors. This technique involves wiping out the hormone receptors or altering their shape. This leaves the hormones unable to attach themselves to the cancer cells and incapable of stimulating growth.

Side effects of hormone therapy

Because hormones play an important role in regulating sexuality, sexual characteristics, and other physiological processes, you’re likely to experience some side effects as a result of hormone therapy. The degree to which you’ll be affected depends in part on the drug or drugs you’re taking and how they’re administered.

Women may experience effects similar to menopause, which is the natural decline in estrogen production that occurs with age. These include weight gain, hot flashes, night sweats, a change in sex drive, and vaginal dryness. Some therapies may also increase the risk of developing blood clots and uterine or endometrial cancer.

Men receiving hormone therapy may experience fatigue, loss of sex drive, impotence, osteoporosis, loss of muscle mass, and enlarged breasts.

It’s important to discuss with your doctor how hormone therapy may affect your quality of life before beginning treatment. There are many complementary therapies and lifestyle adjustments you can make to help manage side effects. Doctors are also exploring new prescription regimens and other strategies to limit some of the side effects of hormone therapy while enhancing its therapeutic effects.

Treating breast cancer

In many types of breast cancer, the growth of cancer cells depends on the female hormone estrogen. To treat these hormone-responsive tumors, doctors prescribe hormone therapy, anticipating that cutting the supply of estrogen will stop the cancer cells from growing or spreading to other parts of the body.

There are a variety of hormone therapies for breast cancer. Medications known as selective estrogen receptor modulators (SERMs) bind to estrogen receptors and block the hormone from reaching cancer cells. Another group of hormone therapy medicines called aromatase inhibitors shut down the production of estrogen. Rather than affect the estrogen receptors, these drugs bind to the aromatase enzyme — the protein that’s responsible for producing estrogen after menopause. This may reduce the supply of estrogen, causing the cancer cells that depend on the hormone to starve, halting their growth and division.

Treating prostate cancer

Many types of prostate cancer are also hormone-responsive, meaning the male hormone testosterone is an essential ingredient to the growth and division of their cells. Depending on the diagnosis, doctors may use different strategies to interrupt a tumor’s supply of testosterone. They may eliminate the main source of male hormones by surgically removing the testicles — an operation known as an orchiectomy. Another form of hormone therapy involves administering the female hormone estrogen, which interferes with the production of testosterone in the testicles. Similarly, other drugs called luteinizing hormone-releasing hormone (LHRH) agonists may reduce testosterone production.

Even with hormone therapy, the adrenal glands continue to produce small amounts of male hormones. Doctors may also prescribe an antiandrogen — a medicine designed to block the effects of any male hormones that remain. Combining these treatments to completely wipe out male hormones is known as a total androgen blockade.