Progestins are used in hormone replacement therapies to counteract the negative effects of estrogen on the uterus and reduce the risk of uterine cancer. However, evidence in recent studies and clinical trials has demonstrated that progestins increase the risk of breast cancer. Now, University of Missouri researchers have compared four types of progestins used in hormone replacement therapies and found significantly different outcomes on the progression of breast cancer in an animal model depending on the type of progestins used.
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