GHK-Cu: One Peptide, Two Very Different Jobs
Skin serum and scalp injection aren't the same use case wearing different packaging — they lean on different sides of what GHK-Cu actually does.
GHK-Cu shows up in two completely different contexts — a topical serum on a skincare shelf, and an injectable used for scalp/hair-density goals — and it's easy to assume one of those is the "real" use and the other is marketing. Mechanistically, both are grounded in the same underlying biology, just applied to different tissue.
GHK-Cu is a copper-carrying tripeptide, and copper itself is a required cofactor for a set of enzymes involved in collagen and elastin crosslinking — the structural proteins that give skin its firmness. Topically, GHK-Cu is studied for stimulating collagen and glycosaminoglycan synthesis at the skin's surface layer, which is the basis for its cosmetic use: better matrix turnover, applied where the matrix actually is.
The scalp/hair use case leans on a different part of the same peptide's profile: GHK-Cu is also studied for modulating gene expression tied to follicle activity and for anti-inflammatory effects locally at the follicle. Because that effect is happening at the level of the hair follicle rather than the skin surface, topical application alone doesn't reliably reach it — which is the actual reason the hair-focused protocol shifts to injection or microneedling instead of a cream, not because injectable versions are simply "stronger."
The throughline is copper delivery and matrix/gene-expression modulation in both cases; the delivery method changes because the target tissue and depth changes, not because the underlying mechanism is different.