Nolvadex decreases GH and IGF-1 production. Part of the gains made in an AS cycle are a direct result of the anabolic / androgen increasing the GH and IGF-1 production. So, yes Nolvadex will hinder gains during a cycle. By how much? I'm not sure, but IMO not a huge amount but enough that I would not use the Nolvadex unless I showed signs of Gyno. Liquidex is better to use during a cycle IMO.