# GHK-Cu — A Medical Literature Index for the Copper Tripeptide > GHK-Cu (Copper Tripeptide-1) is a naturally occurring signaling molecule studied in over 300 published papers. Gene modulation, wound healing, hair growth, and skin research — indexed and cited. A clinical-register digest of the published peer-reviewed literature on GHK-Cu, with every quantitative claim cited to its source. ## What the GHK-Cu literature has established GHK-Cu (Glycyl-L-Histidyl-L-Lysine Copper(II) Complex) is a tripeptide-copper complex first isolated from human albumin by Loren Pickart in 1973, when he observed that old hepatic tissue began synthesizing proteins at youthful rates in the presence of a small molecule from young human plasma. That molecule was GHK. The copper-coordinated form — GHK-Cu — became the subject of more than 300 subsequent publications spanning wound healing, collagen synthesis, hair follicle biology, gene expression, neuroprotection, and gut mucosal repair. The compound is endogenous. Human plasma carries approximately 200 ng/mL of GHK at age 20; that level declines to roughly 80 ng/mL by age 60 [13]. This age-dependent fall is documented in the anti-aging literature as a potential marker of biological aging, though causality has not been established in humans. The mechanism is broad-spectrum. A Connectivity Map analysis using the GHK gene signature found that the tripeptide modulates approximately 31.2% of the human genome — changing expression by 50% or greater — upregulating 59% of affected genes and suppressing 41%, with the upregulated set concentrated in tissue repair, antioxidant defense, and neuronal function [1]. The Ubiquitin-Proteasome System shows the strongest activation: 41 upregulated genes against 1 downregulated [1]. GHK-Cu delivers bioavailable copper(II) to copper-dependent enzymes including superoxide dismutase, ceruloplasmin, and lysyl oxidase — the enzyme responsible for collagen and elastin crosslinking [19]. It has also been proposed to function as a histone deacetylase inhibitor that may partially reverse age-related epigenetic gene silencing [6]. Clinical translation remains early. Topical GHK-Cu has the most controlled human data: an 8-week randomized trial of 40 women found a 55.8% reduction in wrinkle volume (p<0.001) and 32.8% reduction in wrinkle depth (p=0.012) with a nano-carrier formulation [5]. A 6-month RCT in 45 androgenetic alopecia patients showed a hair-count increase of 71.5 in the treatment group versus 9.6 for placebo [7]. Injectable and intranasal GHK-Cu have been studied only in preclinical models as of 2025 — no completed human interventional trials for systemic delivery exist. ## What Is Copper Tripeptide-1 (GHK-Cu)? Copper Tripeptide-1 is the INCI (International Nomenclature Cosmetic Ingredient) name for GHK-Cu — the same molecule under the nomenclature system used on cosmetic product labels. The IUPAC sequence is glycyl-L-histidyl-L-lysine; the copper complex forms when the histidine imidazole nitrogen and the terminal amine together coordinate a copper(II) ion [19]. GHK-Cu's molecular weight is 340.4 Da. It is classified as a carrier peptide — a peptide that delivers a mineral cofactor (copper) to enzymes that require it — but in the GHK-Cu case the biological activity extends far beyond simple mineral transport. The tripeptide is also a signal peptide: it activates TGF-beta pathway signaling, induces fibroblast chemotaxis, and triggers VEGF-mediated angiogenesis [4]. ### What Is a Copper Peptide? A copper peptide is a short peptide sequence that forms a stable complex with copper ions. In the research literature, "copper peptide" most commonly refers specifically to GHK-Cu. The copper coordination is essential for most of the documented biological activity: GHK without copper shows reduced fibroblast-stimulating potency compared to the copper complex, though GHK alone demonstrates metal-sequestration properties relevant to neuroprotection [11]. Cosmetic applications use the Copper Tripeptide-1 INCI designation; research papers use GHK-Cu or PC 1038 (the early laboratory code assigned by Pickart). ## The headline data points Four numbers organize the GHK-Cu evidence base: **~31%** — the fraction of human genes whose expression is changed ≥50% by GHK in the Connectivity Map analysis; 59% of those are upregulated, 41% downregulated [1]. **340.4 Da** — molecular weight of GHK-Cu. Its small size is why topical formulations can achieve dermal penetration without a delivery system, though stability in aqueous solution is a formulation challenge [15]. **200 → 80 ng/mL** — the decline in circulating GHK from age 20 to age 60 in human plasma [13]. This decline pattern is the basis for the anti-aging research hypothesis, not a clinical claim. **55.8%** — wrinkle volume reduction in the 8-week, 40-subject RCT using a topical nano-carrier formulation (p<0.001 vs control) [5]. This is the strongest controlled human efficacy signal in the published literature. For the [GHK-Cu mechanism of action](/research#mechanism) in detail — including the TGF-beta pathway, VEGF upregulation, and HDAC inhibition proposal — see the Research page. For [GHK-Cu hair growth research](/hair-growth) and [copper peptide for skin repair](/skin-research), dedicated pages index the relevant studies separately. ## Regulatory and research classification GHK-Cu is not FDA-approved for any therapeutic indication. It is an approved cosmetic ingredient under the INCI system as Copper Tripeptide-1 — topical cosmetic use does not require FDA pre-market approval. There is no approved injectable formulation for human use and no established human dosing protocol for systemic delivery. Injectable and intranasal GHK-Cu remain at the preclinical stage as of 2025 [15]. GHK-Cu is not currently listed on the WADA Prohibited List. It is not a hormone, a growth factor, or a listed peptide hormone. Consult the current WADA list for definitive status before any competitive-sports context. For [copper peptide side effects](/faq#side-effects) and safety profile — including what the preclinical data shows about copper homeostasis at studied dose ranges — see the [frequently asked questions](/faq). --- A medical-desk index of the peer-reviewed GHK-Cu record — thirty-plus studies indexed, copper-biology cited at the source, no clinic behind the reference shelf.