Hormones are chemical substances that are produced by glands in the body, which enter the bloodstream and cause effects in other tissues. For example, the hormone testosterone is made in the testicles and is responsible for male characteristics such as deepening voice and increased body hair. The use of hormone therapy to treat cancer is based on the observation that receptors for specific hormones that are needed for cell growth are on the surface of some tumor cells. Hormone therapies work by stopping the production of a certain hormone, blocking hormone receptors, or substituting chemically similar agents for the active hormone, which cannot be used by the tumor cell. The different types of hormone therapies are categorized by their function and/or the type of hormone that is affected.
Exemestane is an aromatase inhibitor. This means it blocks the enzyme aromatase (found in the body’s muscle, skin, breast and fat), which is used to convert androgens (hormones produced by the adrenal glands) into estrogen. In the absence of estrogen, tumors dependent on this hormone for growth will shrink.