Wednesday, April 9, 2014

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

I wonder if this has an effect on the proliferation of endometriosis lesions as well?

(BC=breast cancer) "In vitro studies have shown that progestins derived from 19-Nortestosterone exert an estrogen-like proliferative effect on BC cell lines [125,126]. The effect is probably mediated by reduced 5α metabolites, which interact with α and β estrogen receptors [127]. One might also conceive, however, that progestins with androgenic activity stimulate BC cell proliferation via in...teraction with androgen receptors....More importantly, many of the progestins used have several non-progesterone like actions that potentiate the proliferative effect of estrogens on breast tissue and estrogensensitive cancer cells. We therefore suggest that when HRT is indicated, preparations containing progesterone and not a synthetic progestin should be used, according to a sequential or cyclic-combined regimen. In this way the risk of endometrial cancer is minimized without increasing the risk of BC."

 "...We find, as shown previously (), that estradiol is not required for establishment of endometriosis-like lesions.... Finally, endometriosis-like lesion growth is mediated predominately by estradiol signaling via ERα to increase lesion size, fluid volume, increased epithelial cell height, and epithelial cell proliferation...."