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Comment & Response
December 2018

Progestin, Not Progesterone

Author Affiliations
  • 1Hormone Restoration, Tunkhannock, Pennsylvania
JAMA Oncol. 2018;4(12):1786. doi:10.1001/jamaoncol.2018.4637

To the Editor In their article on breast cancer risk in BRCA1 mutation carriers who were given hormone replacement therapy postovariectomy,1 the authors use the word “progesterone” throughout without explanation or qualification. The corresponding author affirmed that most of these women received various progestins, not progesterone.

Progestins, also referred to as progestagens, are invented molecules with structures that are different from human progesterone. They are not progesterone. Calling these molecules progesterone is an all-too-common error of biochemical nomenclature that prevents, rather than promotes understanding.2 The article thereby falsely associates progesterone with breast cancer risk. Many studies and reviewers have indicated that progesterone does not increase breast cancer risk as do many progestins, including medroxyprogesterone.3-5 The greater safety of progesterone with regard to breast cancer risk is a matter of the greatest concern to women who require ovarian hormone replacement therapy.

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