I keep seeing GHK-Cu described as a miracle for skin firmness and fine lines, and separately I see people talk about it in an injectable context. I am trying to understand what the literature genuinely supports versus what is marketing.
From what I have read, most of the human skin data is on topical copper tripeptide creams, and even a lot of that is small studies or in-vitro fibroblast work showing upregulation of collagen and metalloproteinases. Is there any decent controlled human data on visible outcomes, or is it mostly mechanism papers extrapolated forward?
Not asking anyone what to do, just trying to separate the mechanism from the actual outcomes. Links to reviews welcome.