AHK-Cu, the copper peptide sold for hair growth, has one study behind it, and that study grew hair follicles in a dish. GHK-Cu has more than 80 PubMed papers that use the exact term and a handful of small human studies. No study has compared the two.
Here is how they differ, what each has been tested on, and where the claims outrun the data.
They differ by one amino acid
| GHK-Cu | AHK-Cu | |
|---|---|---|
| Sequence | Gly-His-Lys | Ala-His-Lys |
| Free peptide MW | 340.4 (1) | 354.4 (1) |
| CAS (peptide) | 49557-75-7 (1) | 126828-32-8 (1) |
Position one is the only structural difference. GHK starts with glycine, and AHK starts with alanine, which carries one extra methyl group. No published study compares the two, and AHK-Cu’s one paper didn’t measure penetration (3).
GHK is present in human plasma, saliva and urine, and it declines with age. That comes from a 2015 review by Pickart and colleagues at Skin Biology (6).
What the evidence looks like
| GHK-Cu | AHK-Cu | |
|---|---|---|
| PubMed records | About 100 | 1 |
| Randomized human trials | A few, all small (a 2026 review counted two) | None |
| Human hair data | Uncontrolled mixtures and one 18-person eyebrow study | None |
| Head-to-head comparison | None | None |
What GHK-Cu has
A 2026 systematic review of GHK-Cu in aesthetic medicine found 20 studies. Eighteen were preclinical and two were randomized trials (4).
The first trial, in 2006, followed 13 people after laser resurfacing, with or without GHK-Cu. Blinded evaluators found no statistically significant difference in redness, wrinkles or skin quality. A patient questionnaire favored GHK-Cu (p=0.04) (7).
The second, in 2016, tested a GHK-Cu serum in a lipid nano-carrier on 40 women aged 40 to 65 for 8 weeks. The paper reports a 55.8% relative reduction in wrinkle volume against the vehicle and 31.6% more than a Matrixyl 3000 product (8). It was a split-face trial of one formulation.
Wound healing rests mostly on animal and cell work. A 2026 review says the preclinical data consistently support matrix remodeling, epithelial repair and angiogenesis, while the clinical evidence stays sparse. It calls GHK-Cu “promising but unproven” (5). A Phase 2 acute-wound trial is recruiting and has no results yet (5).
What AHK-Cu has
AHK-Cu’s evidence is one paper. In 2007, Pyo and colleagues found it stimulated the elongation of human hair follicles in culture and the proliferation of dermal papilla cells, at concentrations of 10⁻¹² to 10⁻⁹ molar. At 10⁻⁹ molar it reduced the number of apoptotic dermal papilla cells, but the drop wasn’t statistically significant (3).
It’s the only AHK-Cu paper in PubMed. The follicles came from human donors, but nobody was treated with it.
Does GHK-Cu have more hair evidence?
Neither peptide has a controlled human scalp trial. PubMed shows several human scalp reports that included a copper peptide, and all were uncontrolled mixtures. One was a single-arm study of 1,000 people given scalp injections of a formula that also held several growth factors (9). Another was four cases treated with a laser, finasteride, growth factors and a copper peptide (10). A third, in 18,918 men, used an injected solution that held copper tripeptide among more than a dozen ingredients, alongside oral finasteride and minoxidil (12). None of them can isolate what GHK-Cu did. One placebo-controlled trial of 45 men tested a 5-ALA and GHK complex without copper (13).
Two more pieces exist. A 2026 review mentions an 18-person split-face eyebrow study with positive cosmetic hair outcomes. It didn’t define the GHK-Cu form or how much reached the skin (5). And a 1993 review reports that a copper-binding peptide called PC1031 enlarged follicles in fuzzy rats, similar to minoxidil. The macaque work in that review tested other agents: minoxidil, diazoxide and a 5-alpha-reductase inhibitor (2).
Skin penetration
In a lab skin model, microneedle-treated human skin let 134 nmol of GHK peptide and 705 nmol of copper through in 9 hours. Almost none crossed intact skin (11). It was a diffusion experiment on excised skin.
Which one has more evidence?
| Goal | What the evidence shows |
|---|---|
| Wrinkles and firmness | GHK-Cu has two small human trials, and one was negative on objective measures. AHK-Cu has none. |
| Wound healing and scars | GHK-Cu has mostly animal and cell work. AHK-Cu has none. |
| Hair thinning | Neither has a controlled human scalp trial. |
| Using both | No study has tested the combination. |
GHK-Cu leads on volume and on human data. Neither has shown it regrows scalp hair. For the details on each, see our GHK-Cu buyer’s guide and AHK-Cu evidence review, and compare sellers in the best peptide vendors guide.
Frequently Asked Questions
Which is better, AHK-Cu or GHK-Cu?
GHK-Cu has more evidence: more than 80 PubMed papers and a handful of small human studies. AHK-Cu has one lab study. Neither has a controlled human scalp trial.
Has anyone compared them directly?
No. Every comparison is inference across separate research.
Is AHK-Cu better for hair?
That hasn’t been shown. Its one study used human hair follicles in culture.
What is the actual difference?
One amino acid at position one: glycine in GHK, alanine in AHK. Both share the same His-Lys sequence after it.
Can I use both together?
No study has tested the combination.
Is GHK-Cu natural?
GHK is present in human plasma, saliva and urine and declines with age, according to a 2015 review by Pickart and colleagues at Skin Biology.
Can either replace minoxidil or finasteride?
No. Neither has a controlled human scalp trial, and neither is an FDA-approved hair-loss drug.
Educational content only, not medical advice. Neither peptide is FDA-approved to treat hair loss or any condition. Consult a clinician for hair loss or skin concerns.
References
- PubChem: Gly-His-Lys (GHK), CID 73587 and Ala-His-Lys (AHK), CID 7408502
- Uno H, Kurata S. Chemical agents and peptides affect hair growth. J Invest Dermatol. 1993;101(1 Suppl):143S-147S. doi:10.1111/1523-1747.ep12363275
- Pyo HK et al. The effect of tripeptide-copper complex on human hair growth in vitro. Arch Pharm Res. 2007;30(7):834-9. doi:10.1007/BF02978833
- Mokhtar J et al. The regenerative potential of GHK-Cu in aesthetic medicine. Aesthet Surg J. 2026
- Mateescu DM et al. GHK-Cu as a bioactive metallopeptide and drug-delivery cargo. Pharmaceutics. 2026;18(9). doi:10.3390/pharmaceutics18091077
- Pickart L, Vasquez-Soltero JM, Margolina A. GHK peptide as a natural modulator of multiple cellular pathways in skin regeneration. Biomed Res Int. 2015;2015:648108. doi:10.1155/2015/648108
- Miller TR et al. Effects of topical copper tripeptide complex on CO2 laser-resurfaced skin. Arch Facial Plast Surg. 2006;8(4):252-9. doi:10.1001/archfaci.8.4.252
- Badenhorst T et al. Effects of GHK-Cu on MMP and TIMP expression, collagen and elastin production, and facial wrinkle parameters. J Aging Sci. 2016;4(3):166
- Kapoor R, Shome D. Intradermal injections of a hair growth factor formulation for enhancement of human hair regrowth: a first-in-man pilot clinical study. J Cosmet Laser Ther. 2018;20(6):369-79. doi:10.1080/14764172.2018.1439965
- Bertin ACJ et al. Fractional non-ablative laser-assisted drug delivery leads to improvement in male and female pattern hair loss. J Cosmet Laser Ther. 2018;20(7-8):391-4. doi:10.1080/14764172.2017.1418516
- Li H et al. Microneedle-mediated delivery of copper peptide through skin. Pharm Res. 2015;32(8):2678-89. doi:10.1007/s11095-015-1652-z
- Tanaka Y, Aso T, Ono J, Hosoi R, Kaneko T. Androgenetic alopecia treatment in Asian men. J Clin Aesthet Dermatol. 2018;11(7):32-35. PMID 30057663.
- Lee WJ, Sim HB, Jang YH, Lee SJ, Kim DW, Yim SH. Efficacy of a complex of 5-aminolevulinic acid and glycyl-histidyl-lysine peptide on hair growth. Ann Dermatol. 2016;28(4):438-443. PMID 27489425.