Aromatase

Aromatase is an enzyme that removes the C-19 methyl group and oxidizes the 3- and 17-positions of steroids, including reactions that convert androgenic steroids (testosterone) into estrogenic steroids (estrogen). Because some tumors are estrogen-sensitive, aromatase inhibitors are sometimes used to treat cancer, mostly in post-menopausal women because aromatase inhibitors do not block estrogen synthesis in the ovaries.