Hormones are substances produced naturally in the body. They act as chemical messengers and influence the growth and activity of cells. Hormones are produced by a number of different organs and glands, which together are known as the endocrine system.

Hormone therapies work by altering the production or activity of particular hormones in the body. They are most commonly used to treat breast cancer and prostate cancer. The type of hormone therapy given depends on the type of cancer to be treated.

There are several different types of hormone therapy. They are normally given as pills or injections. The side effects can vary and will depend on the individual drug given. General side effects may include tiredness, headaches, and muscle and joint pain.