This is caused by tamoxifen’s ability to up-regulate the progesterone receptor. (54-56) This can dramatically increase the chances of developing gyno in future cycles when utilizing progestin based anabolics such as Nandrolone (Deca) or Trenbolone (or any pro-hormone acting upon the progesterone receptor).
Regardless of any positive effects on fertility or testosterone levels, Clomid and Nolvadex use is highly correlated with erectile dysfunction, libido suppression, and even emotional disorders. (10,47)
Research with male breast cancer patients has also reported decreased libido, and thrombosis associated with tamoxifen use. (47) The thrombotic effect (blood vessel clogging) could explain the mechanism by which SERMs may inhibit erectile function, by reducing circulation to erectile tissue. (47, 52)