# Frequently Asked Questions > FAQ: GHK-Cu, Melanotan II and GLOW — Skin & Aesthetics Research Peptides — Chroma Peptides — Plain answers on Skin & Aesthetics research peptides: what GHK-Cu does, how Melanotan II works, what the melanogenesis cascade is, and what is actually in the GLOW blend — cited throughout. **QUESTIONS** The questions readers actually arrive with, answered from the cited literature rather than from product copy. ## What does a GHK-Cu peptide do? GHK-Cu does two things at once: it carries copper into skin tissue, and it acts as a signal to the cells that build the skin's structural scaffolding. In fibroblast culture it stimulates collagen synthesis starting between 10^-12 and 10^-11 M and peaking around 10^-9 M, without changing cell number — a specific metabolic effect rather than simply more cells [7]. Beyond collagen it stimulates elastin, glycosaminoglycans and decorin, and rebalances matrix metalloproteinases against their inhibitors [4]. Across wound-healing models it raises VEGF, FGF-2 and nerve growth factor while suppressing free radicals, TGF-beta-1 and TNF-alpha [6]. In human topical use, the recurring comparative result is that it increased collagen production in 70% of treated subjects, against 50% for vitamin C and 40% for retinoic acid [1][4]. ## What is GHK-Cu and how does it work? GHK-Cu is the copper(II) complex of the tripeptide glycyl-L-histidyl-L-lysine. The sequence is not synthetic in origin — it occurs inside the alpha-2(I) chain of type I collagen and is released when collagen is broken down, which is why it is often described as an endogenous repair signal. The copper is held at three coordination points, leaving the lysine side chain free. The copper matters mechanically as well as chemically: lysyl oxidase, the enzyme that cross-links collagen and elastin into load-bearing fibres, is copper-dependent, and the tightly bound ion also gives the complex superoxide-dismutase-like antioxidant behaviour. Delivery is the practical constraint, because free GHK is strongly water-loving (clogP -2.24) and the stratum corneum is built to exclude exactly that [1]. When copper is applied as the GHK-Cu complex it does cross human skin, with a permeability coefficient of 2.43 +/- 0.51 x 10^-4 cm/h and a retained dermal depot of 97 +/- 6.6 ug/cm2 over forty-eight hours [5]. ## Is GHK-Cu peptide really anti-aging? The evidence supports something narrower and more interesting than the marketing claim. Plasma GHK does fall with age, from roughly 200 ng/mL at twenty to roughly 80 ng/mL by sixty [4], and topical application in small controlled studies has been associated with improvements in skin laxity, clarity, firmness, density, fine lines and wrinkle depth [4]. Gene-expression analysis reports GHK altering expression of about 31.2% of human genes at a fifty-percent-or-greater change threshold, with 59% raised and 41% suppressed, including strong stimulation of the ubiquitin-proteasome system at 41 genes up against one down [2]. The caveats matter as much as the findings. Human trials are small and topical. A large share of the foundational mechanistic and review literature originates with a single research group, so independent replication of the broader claims is limited [1][4]. And the widely repeated 'about four thousand genes' figure is an extrapolation from the threshold table, which reports on the order of two thousand one hundred genes [2]. The reasonable reading is a genuine, well-described dermal remodelling effect that the anti-aging framing consistently oversells. ## What is the difference between GHK and GHK-Cu? GHK is the bare tripeptide — glycine, histidine, lysine. GHK-Cu is that peptide with a copper(II) ion chelated to it. The distinction is routinely lost in both marketing and the literature, and it is not cosmetic. Most of the documented tissue-remodelling activity depends on the copper being properly coordinated; the free peptide without copper does not reproduce key effects in cell studies. Copper coordination is also what keeps the ion chemically safe: intact GHK-Cu binds copper with a high stability constant, which prevents it from acting as a pro-oxidant. If a product degrades, or is combined with something that strips the copper loose — pure vitamin C at low pH, or exfoliating acids — that protective binding is lost and both actives are wasted [1]. So when a study reports on 'GHK', it is worth checking which form was actually used. ## What is Melanotan 2? Melanotan II is a synthetic cyclic heptapeptide analogue of alpha-melanocyte-stimulating hormone, designed at the University of Arizona in the late 1980s for potent, protease-resistant melanotropic activity. Its sequence is a truncated, cyclised, D-phenylalanine-substituted derivative of the core active region of the natural thirteen-residue hormone. It is not approved by any regulator, anywhere, for any indication, and it should be understood as an unapproved research compound rather than a cosmetic or a medicine. It is frequently confused with two related but distinct molecules that *are* approved: afamelanotide, for the rare light-sensitivity disorder erythropoietic protoporphyria, and bremelanotide, which was derived from Melanotan II and approved for a sexual-desire indication [11]. Those approvals belong to those molecules and their own trial packages. ## What is Melanotan 2 used for in research? In the published record it appears in three broad research contexts, none of them cosmetic tanning. First, sexual function: a double-blind, placebo-controlled crossover study in ten men with psychogenic erectile dysfunction found that a subcutaneous dose of 0.025 mg/kg produced clinically apparent erections in eight of ten, with mean duration of greater-than-80% tip rigidity of 38.0 minutes against 3.0 minutes on placebo, alongside transient nausea, stretching and yawning [12]. Second, appetite and reward neuroscience: bilateral microinjection into the nucleus accumbens of male mice at 0.1 to 1 nmol per side decreased food consumption in home-cage and operant paradigms and reduced appetitive responding for food, without conditioned taste aversion and without altering metabolic rate [9]. Third — and increasingly the dominant category — harm documentation. Recent literature is largely case reports, including reversible oral-mucosal pigmentation after self-administration [8] and renal infarction with a proposed thrombotic or directly toxic renal mechanism [10]. ## How does Melanotan 2 work in the body? It is a non-selective agonist across melanocortin receptors MC1R through MC5R, which is why its effects cannot be confined to skin. At MC1R on melanocytes it raises intracellular cyclic AMP and drives the cascade that upregulates tyrosinase and shifts pigment synthesis toward eumelanin — colour without ultraviolet exposure. At MC4R and MC3R in the hypothalamus and mesolimbic system it alters appetite, energy balance and sexual motivation, which is the isolated effect demonstrated in the nucleus accumbens microinjection work [9]. At MC5R it engages exocrine and sebaceous gland function. That receptor promiscuity is the mechanistic reason the commonly reported nausea, flushing, appetite suppression and spontaneous erections are not incidental side effects but the same compound acting on the same receptor family in different tissues. Preclinical work on alpha-MSH analogue haemodynamics also indicates melanocortin agonists can raise blood pressure, which is consistent with the vascular events described in case reports [10]. ## What is the melanogenesis (MC1R-cAMP-MITF) signaling cascade? It is the chain of events that turns an external signal into pigment inside a melanocyte. A melanocortin ligand — alpha-MSH naturally, or a synthetic analogue such as Melanotan II — binds MC1R, a G-protein-coupled receptor on the melanocyte surface. Binding activates adenylate cyclase, which raises intracellular cyclic AMP. Cyclic AMP activates protein kinase A, which phosphorylates the transcription factor CREB. CREB in turn drives expression of MITF, the master regulator of the pigment cell. MITF then upregulates the melanogenic enzyme battery, tyrosinase foremost among them, and synthesis shifts toward eumelanin, the darker and more photoprotective pigment. Ultraviolet exposure normally reaches this cascade indirectly, by prompting keratinocytes to release alpha-MSH. A synthetic agonist enters the same pathway directly, which is precisely why tanning occurs without sunlight — and why the effect appears wherever melanocytes are, including mucosal tissue that was never the target [8]. Copper is relevant here too, from the other route: tyrosinase is a copper-dependent enzyme. ## What is GLOW peptide? GLOW is not a single peptide. It is a supplier- or clinic-formulated blend of three separate research peptides in one vial, most commonly GHK-Cu, BPC-157 and TB-500. There is no regulatory dossier for it, no reference product, and no analytical standard defining what a vial labelled GLOW contains; ratios are formulation-specific and not standardised. No controlled clinical trial of the combination exists for any indication. Every efficacy claim made for it is borrowed from research on the individual constituents, much of it preclinical, plus a mechanistic argument that the three should complement each other. The peer-reviewed review that names all three constituents together concludes that while many unapproved peptides show favourable tissue-repair outcomes in animal models, rigorous human safety data are scarce and there is potential for serious harm [13]. ## What does the GLOW peptide do? The combination thesis is that each constituent covers a different part of repair. GHK-Cu supplies matrix remodelling — collagen, elastin, glycosaminoglycans, decorin, and rebalanced metalloproteinases [4][6]. BPC-157 supplies vascular and cytoprotective activity; it is pro-angiogenic via VEGFR2, increasing VEGFR2 expression, promoting receptor internalisation in endothelial cells and activating the VEGFR2-Akt-eNOS pathway with increased vessel density in vivo and in vitro [15]. TB-500 supplies cell-mobility and anti-scarring activity by sequestering G-actin. What the blend *does* in humans is unmeasured. No study has tested the three-peptide combination against its own parts, so whether the interaction is synergistic, additive or interfering is unknown, and the three peptides clear at very different rates when mixed into one injection. The most data-poor constituent, BPC-157, has only three small human pilot studies behind it and is described in its own 2025 review as investigational and to be approached with caution [14]. A blend cannot be better evidenced than its least-evidenced part. ## What does GLOW peptide have in it? Three peptides, from three unrelated research literatures. **GHK-Cu** — the copper(II) chelate of glycyl-L-histidyl-L-lysine, the matrix-remodelling copper tripeptide that in topical form is a legal cosmetic ingredient under the INCI name Copper Tripeptide-1. **BPC-157** — a synthetic stable pentadecapeptide, sequence GEPPPGKPADDAGLV, derived from a gastric body-protection protein and studied as cytoprotective and pro-angiogenic. In 2023 the FDA placed it in a category of bulk drug substances identified as not eligible for pharmacy compounding pending further evaluation. **TB-500** — the acetylated heptapeptide Ac-LKKTETQ, corresponding to the actin-binding region of thymosin beta-4. Ratios vary by source and are unverified outside formal analysis; the fixed milligram ratios circulating in community protocols have no basis in controlled human trials. The blend is prohibited for tested athletes because thymosin beta-4 is named on the WADA Prohibited List [13]. ## What peptides are in the GLOW blend, and does a legal cosmetic ingredient make the blend legal? The blend contains GHK-Cu, BPC-157 and TB-500 — and the second half of the question is the one that matters most. It does not. Regulatory status attaches to a route and a claim, not to a molecule. Topical Copper Tripeptide-1 is a permitted cosmetic ingredient, which is a statement about using that ingredient in a cosmetic product sold on appearance claims. The same molecule reconstituted for injection is outside that register entirely, and GHK-Cu has no approved therapeutic indication by any route in any jurisdiction. Status in a mixture also travels upward in strictness, never downward. The most permissive constituent cannot make the vial permissive: BPC-157 and TB-500 are unapproved research chemicals, both are prohibited in tested sport, and the presence of a WADA-listed thymosin beta-4 fragment sets the anti-doping status of the whole blend regardless of how skin-focused the framing is [13]. One further identity note worth carrying: most of the efficacy data attributed to TB-500 was generated with full-length thymosin beta-4, not the seven-residue fragment actually sold under that name, and it is not established that the fragment reproduces the parent protein's effects. --- A reading desk for the colour chemistry of skin: Chroma Peptides annotates the published record on copper peptides and melanocortin analogues, and has nothing to sell, nothing to prescribe, and no dose to recommend.