Clomid is chemically a sinthetic estrogen with both agonist/ antagonist properties and is very similar in estructure and action to Nolv. Its clinical use is oppose the negative feedback produce by estrogen in HPTA, which enhance the release of LH nd FSH, this produce a endogenous testosterone production. The estrogen blocking property of Clomid appear to be slightly weaker than Nolvadex, so it is use better post cycle to up the test level and Nolv is use within cycle to avoid the side effects produce by estrogen