- A substance that can prevent the full expression of estrogen. Antiestrogens act by exerting antagonistic effects on target tissues (androgens and progestogens act in this way) or by competing with estrogens for access to receptor sites located on the cell surface. For example, the drug tamoxifen (brand name: Nolvadex) is an antiestrogen that is used in the treatment of breast cancer and to reduce the breast cancer incidence in high-risk women.
* * *Any substance capable of preventing full expression of the biological effects of estrogenic hormones on responsive tissues, either by producing antagonistic effects on the target tissue, as androgens and progestogens do, or by competing with estrogens at estrogen receptors at the cellular level ( e.g., tamoxifen).
* * *an·ti·es·tro·gen or chiefly Brit an·ti·oes·tro·gen -'es-trə-jən,Brit -'ēs- n a substance that inhibits the physiological action of an estrogenan·ti·es·tro·gen·ic or chiefly Brit an·ti·oes·tro·gen·ic -.es-trə-'jen-ik,Brit -.ēs- adj
* * *an·ti·es·tro·gen (an″te-esґtrə-jen) a substance capable of inhibiting the biological effects of estrogens.
Medical dictionary. 2011.