Aromatase inhibitors are a type of hormone therapy drug used to treat breast cancer in women who have gone through a natural menopause (when periods stop). It can also be used in premenopausal women having ovarian suppression (treatment to stop the ovaries working).
Before the menopause, oestrogen is mainly produced in the ovaries. After the menopause, the ovaries no longer produce oestrogen, but some oestrogen is still made in body fat. This process involves an enzyme (a type of protein) called aromatase.
Aromatase inhibitors stop this enzyme from working. This means there’s less oestrogen in the body to help breast cancer cells to grow.