Hormone therapy treats prostate cancer by lowering the level of certain hormones in the body. These hormones are called androgens. Prostate cancer needs androgens to grow. The main androgen is testosterone. Reducing the level of testosterone can slow the growth of prostate cancer and even shrink the tumours.

The testicles make most of the body's testosterone. Hormone therapy can be done in two ways.

• It is often done with medicines. These medicines stop the testicles from making testosterone or they block it.
• Less often, surgery is done to remove the testicles. (This is called an orchiectomy.)

Both types of hormone therapy can cause serious side effects. These include a greater chance of getting osteoporosis, heart disease, and diabetes.

Hormone therapy may also be called androgen deprivation therapy (ADT) or androgen suppression therapy.