Progestins and progesterone in hormone replacement therapy and the risk of breast cancer.

Authors: Campagnoli C, Clavel-Chapelon F, Kaaks R, Peris C, Berrino F.

Publication Year: 2005

Citation: J Steroid Biochem Mol Biol 2005; 96(2):95-108.

The authors discuss the non-progesterone-like effects of synthetic progestins, which can contribute to the increased risk of breast cancer when these are used as part of a combined hormone therapy regimen.  In contrast, bioidentical progesterone does not increase the risk of breast cancer, consistent with experimental in vivo data that shows progesterone has no adverse effect on breast tissue.

http://www.ncbi.nlm.nih.gov/pubmed/15908197