 Cyproterone binds to ARs that are expressed by prostate cancer cells as well as to the AR that are expressed in the hypothalamus and pituitary.Therefore, cyproterone blocks the negative feedback of androgens at the hypothalamic-pituitary level leading to increased luteinizing hormone (LH) serum levels.This rise in LH levels causes an increase in serum testosterone levels and ultimately diminishes the ability of cyproterone to compete for AR binding and to block androgenic stimulation.