How does arimidex (anastrozole) work?

Lower estrogen: It's an aromatase inhibitor. It blocks the enzymatic conversion of androgens (male hormone) to estrogen, thereby lowering estrogen level. It is used to treat breast cancer.

Lowers Estrogen: Arimidex (anastrozole) blocks the production of estrogen by the ovaries, fat cells, and adrenal glands. It thereby lowers the estrogen level in the body. Some breast cancer cells have estrogen receptors. Estrogen spurs these cells to grow, so lowering the amount of it around "staves" the bad cells of their signal to grow. This causes some cells to peter out and die and other's growth to slow down.