GHK-Cu is glycyl-L-histidyl-L-lysine bound to a copper ion. Pickart isolated the tripeptide from human plasma in 1973, noticing that it promoted survival of liver tissue in culture, and the copper binding was worked out shortly after. Plasma levels are around 200 ng per ml at age 20 and fall to about 80 ng per ml by 60, a decline that is frequently cited as the rationale for supplementing it and which is, on its own, only a correlation.

Mechanism, briefly

The histidine and glycine residues form a high-affinity copper(II) binding site. Copper is a required cofactor for lysyl oxidase, the enzyme that cross-links collagen and elastin fibrils, and for superoxide dismutase. GHK-Cu appears to act partly as a copper delivery vehicle to these enzymes and partly through direct signalling: gene expression work by Pickart and colleagues using the Broad Institute Connectivity Map reported that GHK modulated expression of over 4000 human genes, shifting many toward a younger expression profile, including upregulation of collagen types 1, 2 and 4 and of decorin, and downregulation of several inflammatory mediators.

The gene expression work is in cultured fibroblasts. It is interesting and it is not evidence of a clinical outcome.

The skin data, which is genuinely decent for this category

Several small controlled human trials exist, and they measured things rather than asking participants how they felt.

Leyden and colleagues ran a 12 week facial trial of a GHK-Cu containing cream in 71 women with photoaged skin, reporting improvements in fine lines, wrinkle depth, skin clarity and density versus placebo on both expert grading and instrumental measurement. A parallel eye area study in 41 subjects showed reduced fine lines and improved appearance versus both placebo and a vitamin K containing comparator. Finkley and colleagues studied a copper peptide facial product in 67 women over 12 weeks with similar directional results.

Separately, GHK-Cu has been used clinically in wound healing. Studies in diabetic ischaemic ulcers reported improved closure rates and reduced infection, and the peptide has been studied in surgical wound contexts.

The honest reading: multiple independent small trials with objective endpoints pointing the same direction is a real evidence base by cosmetic ingredient standards. It is not the same as a large multicentre randomised trial, sample sizes are in the tens, and several of these studies were funded by companies with a commercial interest in the ingredient. Effect sizes on wrinkle measures are modest, in the range where you need instrumentation to be confident, not the range where people ask what you have done to your face.

The hair data, which is thin

Here the gap between claim and evidence widens considerably.

What exists: GHK-Cu and related copper peptide complexes increase hair follicle size in cultured follicles and in mouse studies, and Pyo and colleagues reported GHK-Cu stimulating follicle proliferation, with an effect attributed partly to vascular endothelial growth factor upregulation. Some copper peptide derivatives were investigated for hair growth in the 1990s, and there is patent literature.

What does not exist: an adequately powered randomised placebo-controlled trial of topical GHK-Cu in androgenetic alopecia with hair count as the primary endpoint. There is no equivalent of the minoxidil or finasteride trial data. The published human hair work is largely small, uncontrolled, or looks at GHK-Cu as one component of a multi-ingredient formulation, which makes attribution impossible.

Anyone selling GHK-Cu specifically for hair regrowth is extrapolating from mouse follicles and mechanism. It may work. Nobody has properly tested it.

Practical use

  • Topical concentrations in studied products are typically 0.05 to 2 percent, with most cosmetic serums in the 1 to 3 percent range. Higher is not established as better and above about 2 percent irritation reports increase.
  • Applied to clean skin, usually once or twice daily. The blue colour is the copper complex and is normal.
  • Timelines from the trials are 8 to 12 weeks before measurable change, consistent with dermal collagen turnover being slow. Anyone promising a two week result is not describing collagen biology.
  • Do not layer GHK-Cu with direct acids or high-strength vitamin C in the same application. Low pH destabilises the copper complex, and ascorbic acid can reduce copper(II) to copper(I), which changes the chemistry entirely and can generate reactive oxygen species. Use them at different times of day.
  • Retinoids are generally fine alongside, at a different time of day.

Injectable GHK-Cu

Some suppliers sell GHK-Cu for subcutaneous injection. The human evidence base described above is entirely topical. Systemic administration of a copper-carrying peptide raises a different question, which is copper load, and copper toxicity is a real clinical entity affecting the liver and neurological function. There is no human dosing study establishing a safe systemic range. Injecting it is not supported by the data people cite when they sell it.

Summary of where evidence stands

Topical facial use for photoaged skin has several small positive controlled trials with objective endpoints, which is more than most peptides in skincare can show, tempered by small samples and industry funding. Wound healing has supportive clinical use. Hair growth has mouse data and mechanism only. Systemic injection has essentially nothing.