# GHK-Cu: The Copper-Peptide Research, Boxed and Cited > GHK-Cu is a copper-binding tripeptide naturally present in human plasma that stimulates collagen, elastin and decorin synthesis in dermal fibroblasts. The published literature, plainly summarized. A loud, plain-spoken digest of the copper-tripeptide literature: every collagen study, skin trial and hair-count result, stacked and cited. ## What the GHK-Cu literature has measured GHK-Cu is a copper-binding tripeptide naturally present in human plasma, saliva and urine. It is the copper(II) complex of glycyl-L-histidyl-L-lysine (MW 402.92, CAS 89030-95-5), and the sequence occurs endogenously inside the alpha-2(I) chain of type I collagen and in SPARC/osteonectin. In human fibroblast cultures GHK-Cu stimulated collagen synthesis dose-dependently, with the effect beginning between 10^-12 and 10^-11 M, peaking near 10^-9 M, and occurring without any change in cell number — a specific metabolic effect, not just more cells [1]. The compound was first isolated in 1973 by Loren Pickart as a plasma factor that caused aged human liver tissue to synthesize proteins like younger tissue [2]. Plasma GHK declines with age — from approximately 200 ng/mL at age 20 to approximately 80 ng/mL by age 60 [3]. That decline, and the breadth of what the molecule does at picomolar-to-nanomolar concentrations, is why GHK-Cu reads across the literature as both a copper chaperone and a signaling molecule. This site indexes that literature. Every quantitative claim on every page maps to a numbered citation. We summarize what was measured, in which model, at which dose — and we name the gaps, of which there are several. ## What Is Copper Tripeptide-1 (GHK-Cu)? Copper tripeptide-1 is the INCI (cosmetic-ingredient) name for GHK-Cu — the label used to declare copper-peptide content in skincare. Chemically it is the copper(II) chelate of the tripeptide glycyl-L-histidyl-L-lysine: the Cu(II) ion is coordinated through the histidine imidazole nitrogen, the glycine alpha-amino nitrogen and the deprotonated glycine-histidine amide nitrogen, leaving the lysine side chain free [3]. The copper ion is not incidental. It enables lysyl-oxidase-mediated collagen and elastin cross-linking and superoxide-dismutase-like antioxidant activity, while the peptide directly signals fibroblasts to remodel the extracellular matrix [6]. The complex is also chemically tight: its copper stability constant is approximately log K 16.4, far higher than free GHK, which limits pro-oxidant free-copper release [3]. ### What is GHK-Cu and how does it work? GHK-Cu is the copper(II) complex of the tripeptide glycyl-L-histidyl-L-lysine, naturally present in human plasma [3]. The copper ion enables lysyl-oxidase collagen cross-linking and superoxide-dismutase-like antioxidant activity, while the peptide directly signals fibroblasts to remodel the extracellular matrix [6]. ### What Is a Copper Peptide? A copper peptide is a short amino-acid chain that binds a copper(II) ion to form a single coordinated complex. GHK-Cu is the most-studied example — three amino acids (glycine, histidine, lysine) carrying one copper. In study models the copper-bound form drives most documented tissue-repair activity; the free peptide does not reproduce MMP-2 stimulation in fibroblast cultures [1]. The form a study used therefore matters, and this digest tracks it throughout. ### What does a GHK-Cu peptide do? GHK-Cu acts as both a copper chaperone and a signaling molecule. At picomolar-to-nanomolar concentrations it stimulates dermal fibroblast synthesis of collagen, elastin, glycosaminoglycans and decorin, rebalances matrix metalloproteinases against their TIMP inhibitors, and modulates antioxidant and wound-repair gene programs [6]. The same review documents upregulation of VEGF, FGF-2 and neurotrophins alongside suppression of free radicals, TGF-beta-1 and TNF-alpha [6]. ### What is the difference between GHK and GHK-Cu? GHK is the free tripeptide (MW 340.38, CAS 49557-75-7); GHK-Cu is its copper(II) chelate (MW 402.92, CAS 89030-95-5) [3]. Copper coordination is required for most documented tissue-repair activities — the free peptide does not reproduce MMP-2 stimulation in fibroblast cultures [1]. Because many studies use free GHK and report systemic or gene-level effects, the form a study tested should always be checked before its findings are generalized to the chelate. ## Why a copper peptide carries this much research GHK-Cu is unusual among studied peptides because it does two jobs at once. The peptide is a signal; the copper is a tool. The peptide scaffold tells fibroblasts to build matrix, and the bound copper(II) is the cofactor lysyl oxidase uses to cross-link the collagen and elastin those fibroblasts make [6]. Strip the copper and most of the documented activity goes with it — the free peptide does not reproduce MMP-2 stimulation in fibroblast cultures [1]. The complex is also chemically disciplined, which is part of why it has a marketed cosmetic safety record. Its copper stability constant of approximately log K 16.4 holds the copper tightly enough to limit pro-oxidant free-copper release [3], and the blue-violet color of a correctly reconstituted solution is the expected Cu(II) absorption signature of an intact 1:1 complex — a brown or green shift signals oxidation or precipitation instead [3]. Stability peaks near pH 5-6.5 [3]. The research also reaches well beyond cosmetics. In rodent systemic models, GHK has been administered intraperitoneally in pulmonary emphysema, fibrosis and silicosis studies and by oral gavage in a DSS-colitis model, with the antioxidant Nrf2/Keap1 axis, NF-kB suppression and the SIRT1/STAT3 pathway recurring across those programs [3]. Those routes and models are described on the [GHK-Cu collagen and gene-expression research](/research) and dosage pages strictly as research context, never as a human protocol. ## Two applications, one molecule The best-documented GHK-Cu research clusters into two application domains. The first is skin: collagen, elastin and decorin synthesis, the matrix-metalloproteinase rebalance against TIMP inhibitors, and the topical-delivery problem that follows from the peptide being highly hydrophilic (clogP -2.24) [11]. The detail lives on the [copper peptide skin research](/skin-research) page, including the dermal copper depot that makes topical delivery work. The second is hair. A 6-month controlled trial in 45 men and a 2024 enhanced-delivery animal study form the strongest signals, and both point to a non-androgenic mechanism rather than DHT blockade [4][14]; the [copper peptide hair growth research](/hair-research) page weighs both, including their formulation caveats. For mechanism, the roughly 31% gene-expression signature and the comparison literature, see the [GHK-Cu collagen and gene-expression research](/research) page. For safety, the vitamin-C incompatibility and the human-data gaps, see [copper peptide side effects and downsides](/faq). One honesty note carried throughout: a large share of the foundational GHK-Cu mechanistic literature originates with a single investigator and colleagues, so independent replication of the broader gene-expression and anti-aging claims is still limited [4]. --- The copper-peptide literature boxed and stacked — every collagen figure, hair count and stability constant logged to its study, with no clinic behind the borders and nothing here on the shelf.