Source:http://linkedlifedata.com/resource/umls/id/C1510932
NCI: A substance that blocks the activity of a progestin.,NCI: A substance that prevents cells from making or using progesterone (a hormone that plays a role in the menstrual cycle and pregnancy). Antiprogestins may stop some cancer cells from growing and they are being studied in the treatment of breast cancer. An antiprogestin is a type of hormone antagonist.