You could certainly run HGH during PCT ... it won't hurt anything, but as mentioned it takes a considerable amount of time for HGH to have a significant effect on your circulating IGF-1 levels ... and that is the part of HGH that is going to equate to muscle gains.
In an ideal situation, you would begin taking HGH several weeks before you begin your AAS portion of your cycle. You would take it all through your AAS cycle and then through PCT (and beyond if you like). Used this way it would probably help you. Beginning it during PCT isn't going to protect (or enhance) your gains right away as something like LR3 IGF-1 would. HGH is great, but it takes time.