estrogen blocker
(ES-truh-jin BLAH-ker)
A substance that keeps cells from making or using estrogen (a hormone that plays a role in female sex characteristics, the menstrual cycle, and pregnancy). Estrogen blockers may stop some cancer cells from growing and are used to prevent and treat breast cancer. They are also being studied in the treatment of other types of cancer. An estrogen blocker is a type of hormone antagonist. Also called antiestrogen.