GHK-Cu is unusual in the peptide world because it actually shows up in cosmetic science literature, not just bodybuilding forums. I have seen it in peer-reviewed work on skin remodeling and it is an ingredient in commercial serums. That makes me more curious than usual about where the evidence is solid and where it is being oversold.
My read is that the topical/cosmetic data on collagen and skin appearance is the most defensible part, while the systemic 'anti-aging' and hair claims are a big leap beyond what has been shown. Linking the Library page for the compiled references.
Is that a fair characterization, or is there better systemic evidence than I have found?