Advanced prostate cancer includes cancer that has spread, cancer that has returned after treatment, and cancer that continues to grow or spread despite treatment or while under surveillance. Because androgens (male sex hormones), such as testosterone, help the growth of prostate cancer, lowering the levels of androgens helps slow the growth of prostate cancer. Androgen deprivation therapy (ADT) is a hormone therapy that slows the growth of prostate cancer by lowering the levels of androgens or blocking the androgens from getting to the prostate cancer cell.

ADT includes the following treatments:

• Bilateral orchiectomy is the surgical removal of the testicles, the main source of testosterone production. Although this treatment is surgery, it is considered hormone therapy because it effectively removes most of the testosterone from the body. This treatment is also called surgical castration.
• Luteinizing hormone-releasing hormone (LHRH) agonists are drugs that lower the body's production of testosterone by stopping the testicles from making testosterone. These drugs are usually given as injections. This treatment is sometimes called medical castration.
• Anti-androgen drugs prevent the body from using testosterone. These drugs are in the form of a pill.
• Combined androgen blockade (CAB) is a treatment strategy to eliminate any remaining androgens in the body. It is a combination of an anti-androgen drug and either surgery or an LHRH agonist drug. Surgical or medical castration eliminates about 90% to 95% of the body's testosterone, and adding the anti-androgen eliminates the remaining 5% to 10% of the body's testosterone.

Some common side effects of hormone therapy may include:

• Psychological effects resulting from testicle removal
• Loss of sex drive
• Impotence (inability to have erections)
• Hot flashes
• Tiredness
• Mood changes
• Muscle shrinkage
• Enlarged and/or tender breasts
• Osteopenia and osteoporosis (loss of bone mass, which may result in a broken bone)
• Weight gain

Some uncommon or rare side effects of hormone therapy include:

• Rise in cholesterol
• Diabetes
• Heart disease
• Liver damage (rare)

Many of these side effects are treatable, and most side effects go away once treatment is finished, except those resulting from an orchiectomy, which are permanent. Men who have received an LHRH agonist drug for more than two years frequently experience persistent side effects for more than one year after the drug is discontinued, and some men never fully recover. In addition, recent research suggests that LHRH agonist therapy may also increase a man's risk of heart disease, heart attack, and death from cardiac arrest (sudden loss of heart function).