Why do we give anti-estrogen drugs to post-menopausal women with breast cancer?

Anti-estrogen drugs: Anti-estrogen drugs are given to both premenopausal and postmenopausal women whose cancer is estrogen receptor-positive or progesterone receptor-positive. These cancer may grow when exposed to estrogen. Anti-estrogen medications block or reduce estrogen that is normally produced by the ovaries in premenopausal women or by fat cells, liver, adrenal glands or other organs in postmenopausal women.