Male hormones (androgens) can cause prostate cancer to grow. Hormone therapy keeps prostate cancer cells from getting the male hormones they need to grow. The testicles are the body's main source of the male hormone testosterone. The adrenal gland makes other male hormones and a small amount of testosterone. Hormone therapy uses drugs or surgery:

• Drugs: Your doctor may suggest a drug that can block natural hormones:
  • Luteinizing hormone-releasing hormone (LH-RH) agonists: These drugs can prevent the testicles from making testosterone. Examples are leuprolide, goserelin, and triptorelin. The testosterone level falls slowly. Without testosterone, the tumor shrinks, or its growth slows. These drugs are also called gonadotropin-releasing hormone (GnRH) agonists. 
  • Antiandrogens: These drugs can block the action of male hormones. Examples are flutamide, bicalutamide, and nilutamide
  • Other drugs: Some drugs can prevent the adrenal gland from making testosterone. Examples are ketoconazole and aminoglutethimide.
  • Orchiectomy: Surgery to remove the testicles is called orchiectomy.

An LH-RH agonist may make your symptoms worse for a short time at first. This temporary problem is called "flare." To prevent flare, your doctor may give you an antiandrogen for a few weeks along with the LH-RH agonist.

An LH-RH agonist such as leuprolide can increase body fat, especially around the waist. The levels of sugar and cholesterol in your blood may increase too. Because these changes increase the risk of diabetes and heart disease, your health care team will monitor you for these side effects.

Antiandrogens (such as nilutamide) can cause nausea, diarrhea, or breast growth or tenderness. Rarely, they may cause liver problems (pain in the abdomen, yellow eyes, or dark urine). Some men who use nilutamide may have shortness of breath or develop heart failure. Some may have trouble adjusting to sudden changes in light.

If used for a long time, ketoconazole may cause liver problems, and aminoglutethimide can cause skin rashes.

Doctors usually treat prostate cancer that has spread to other parts of the body with hormone therapy. For some men, the cancer will be controlled for two or three years, but others will have a much shorter response to hormone therapy. In time, most prostate cancers can grow with very little or no male hormones, and hormone therapy alone is no longer helpful.

At that time, your doctor may suggest chemotherapy or other forms of treatment that are under study. In many cases, the doctor may suggest continuing with hormone therapy because it may still be effective against some of the cancer cells.

Hot flashes, impaired sexual function, loss of desire for sex, and weakened bones may occur in men treated with hormone therapy. Your doctor can suggest medicines that may reduce your risk of bone fractures. Other side effects include diarrhea, nausea, and pruritus (itching).