Peptides for hair loss: what the trials show

The baseline: what proven treatments achieve

Any claim about a hair peptide has to be measured against what the standard treatments already do, and those treatments have large, long trials. In two one-year trials of 1,553 men aged 18 to 41 with male-pattern hair loss, finasteride 1 mg a day by mouth improved scalp hair by every measure. In a one-inch circle of balding crown scalp that started with about 876 hairs, finasteride-treated men had 107 more hairs than the placebo group at one year and 138 more at two, while men on placebo kept losing hair ¹. Topical minoxidil has a similar record. In a 48-week trial of 393 men, 5% minoxidil twice daily was clearly better than 2% minoxidil and placebo, producing 45% more regrowth than the 2% solution, with a faster response and more itching and irritation ².

Those numbers matter for two reasons. They show the size of effect a real treatment produces in well-run trials, and they show the kind of trial needed to prove it: hundreds of people, a placebo, a year or more, and objective hair counts. Very little in the peptide world meets that standard.

What is in a peptide hair serum

Hair serums are sold on a list of named actives, many of them branded ingredient blends. A 2025 review of the most heavily marketed topical hair actives, including Redensyl, Procapil, Capixyl and AnaGain, found that most had been studied in combination with other agents, in trials with small samples, no comparison against standard therapies, mismatched groups, unclear types of hair loss and conflicts of interest ³. The review concluded they might serve as add-ons or for people who cannot tolerate standard treatment, not as replacements ³. That is the frame for everything below: the question is not whether these ingredients do anything, but whether the evidence is good enough to tell.

Capixyl and acetyl tetrapeptide-3

Capixyl is a blend built around acetyl tetrapeptide-3 and biochanin A, an isoflavone from red clover. The strongest trial we found tested a combination of biochanin A, acetyl tetrapeptide-3 and ginseng extracts against 3% minoxidil in 32 men and women with mild to moderate androgenetic alopecia, applied twice daily for 24 weeks in a triple-blind design. Terminal hair counts rose by 8.3% with the herbal combination and 8.7% with minoxidil, a difference that was not statistically significant; one person on minoxidil developed scalp eczema, and none on the combination had a local reaction ⁴.

That is a respectable result for a cosmetic ingredient, and it is also easy to over-read. The comparator was 3% minoxidil, weaker than the 5% concentration shown to outperform lower strengths ²; the trial was small enough that a real difference could have been missed; and it tested a mixture, so it cannot say what the peptide contributed on its own. The authors themselves called for larger, longer studies ⁴.

GHK-Cu and copper peptides

GHK-Cu Low, the copper tripeptide in many serums, is the peptide with the longest research history, almost all of it on skin. For hair, the human evidence is thin and tangled with other ingredients. A report of four patients treated with a fractional laser followed by topical finasteride, several growth factors and 1% copper peptide described improved regrowth in all four ⁵; with a laser, finasteride and growth factors in the mix, the copper peptide's part cannot be separated. An open-label study in India gave 1,000 patients scalp injections of a formulation containing four growth factors, thymosin beta-4 and copper tripeptide-1 every three weeks, and reported less hair fall in 83% and a significant rise in hair count at one year; it had no control group ⁶. A 2026 review of GHK-Cu notes a newer 18-person split-face eyebrow study that reported positive cosmetic hair outcomes but did not establish what form of the peptide was present or how much reached the follicles ⁷.

Laboratory work supports a plausible mechanism without proving an effect on hair. In cultured human keratinocytes and skin models, copper-free GHK increased markers of stemness and proliferation in basal cells, similar to the copper complex ⁸. The broader point from the 2026 review applies here too: GHK-Cu products rarely define the chemical state of the copper peptide, which makes it hard to know what any study actually tested ⁷. Our guide to copper peptides for skin covers the rest of its evidence.

PTD-DBM: the research peptide everyone mentions

PTD-DBM comes from a Korean research group studying a protein called CXXC5, which acts as a brake on the Wnt/beta-catenin pathway that drives hair follicle growth. In a 2017 study, CXXC5 was found raised in shrunken follicles of human balding scalps, mice lacking it regrew hair faster, and a competitor peptide that blocks CXXC5's binding to a partner protein, Dishevelled, activated Wnt signalling and accelerated hair regrowth and the formation of new follicles after wounding in mice ⁹. A 2023 study by the same group named the peptide PTD-DBM and found that it reversed hair loss caused by prostaglandin D2 in mice, and that blocking CXXC5 also eased hair loss driven by DHT, the hormone behind male-pattern loss ¹⁰.

It is a well-built line of research, and it is entirely preclinical. A search of ClinicalTrials.gov on October 3, 2026 found no registered study of PTD-DBM or of KY19382, a related small molecule from the same group ¹¹. The group's corporate affiliations are disclosed on the papers ^{9 10}. Anything sold online as PTD-DBM is an untested research chemical: there is no human dose, no human safety data and no evidence that it regrows human hair.

Thymosin beta-4 and growth-factor mixtures

Thymosin beta-4 Medium appears in some injected hair formulations, such as the one in the 1,000-patient Indian study, alongside growth factors and copper tripeptide ⁶. That study cannot show what any single ingredient did, and it lacked a comparison group. Clinics offering scalp injections of peptide mixtures are offering procedures whose components have not been tested individually for hair, and our TB-500 article explains why thymosin beta-4 and the fragment sold as TB-500 are not the same molecule.

How to judge a peptide hair product

Four questions sort the evidence quickly. Was the ingredient tested alone, or only inside a blend? Was there a placebo or a standard treatment as comparator, and if so, which strength? How many people, for how long, and were hairs counted objectively or rated from photographs? And who ran the study? Most peptide hair actives fail at least two of these ³. Against that, finasteride and 5% minoxidil have placebo-controlled trials in hundreds of people over a year or more ^{1 2}.

None of this means peptide serums are useless. A product that is well tolerated and might add a little to a standard treatment can be a reasonable choice for someone who cannot use minoxidil or finasteride, which is roughly what the 2025 review suggests ³. It does mean that a serum is not a substitute for a proven treatment, and that hair loss with an unclear cause, sudden onset or patchy pattern should be seen by a dermatologist, because it may not be androgenetic at all.

Frequently asked questions

Do peptides help hair growth?

The evidence is weak. The best trial of a peptide blend (acetyl tetrapeptide-3 with biochanin A and ginseng) matched 3% minoxidil in 32 people over 24 weeks. No peptide has trials comparable to finasteride or 5% minoxidil.

Does GHK-Cu regrow hair?

Not proven. Its hair evidence is a four-patient case series combined with other treatments, a single-arm injected mixture and a small eyebrow study, plus laboratory work.

What is PTD-DBM?

A research peptide that blocks the protein CXXC5 and activates Wnt signalling. It regrew hair in mice, but no human trial was registered on ClinicalTrials.gov as of October 3, 2026.

Is Capixyl as good as minoxidil?

In one 32-person trial, a Capixyl-type combination matched 3% minoxidil over 24 weeks, but 5% minoxidil is stronger and the trial was too small to rule out a difference.

Related on Grey Peptides

• GHK-Cu
• Copper peptides for skin
• Copper peptides with vitamin C, retinol or acids

Sources

1. Kaufman, K. D., et al. (1998). Finasteride in the treatment of men with androgenetic alopecia. Finasteride Male Pattern Hair Loss Study Group. J Am Acad Dermatol, 39(4 Pt 1), 578-89. PMID: 9777765
2. Olsen, E. A., et al. (2002). A randomized clinical trial of 5% topical minoxidil versus 2% topical minoxidil and placebo in the treatment of androgenetic alopecia in men. J Am Acad Dermatol, 47(3), 377-85. PMID: 12196747
3. Bikash, C. (2025). Topical Alternatives for Hair Loss: Beyond the Conventional. Int J Trichology, 17(1), 13-19. PMID: 40654553
4. Lueangarun, S., et al. (2020). An Herbal Extract Combination (Biochanin A, Acetyl tetrapeptide-3, and Ginseng Extracts) versus 3% Minoxidil Solution for the Treatment of Androgenetic Alopecia: A 24-week, Prospective, Randomized, Triple-blind, Controlled Trial. J Clin Aesthet Dermatol, 13(10), 32-37. PMID: 33584955
5. Bertin, A. C. J., et al. (2018). Fractional non-ablative laser-assisted drug delivery leads to improvement in male and female pattern hair loss. J Cosmet Laser Ther, 20(7-8), 391-394. PMID: 29452017
6. Kapoor, R., et al. (2018). Intradermal injections of a hair growth factor formulation for enhancement of human hair regrowth - safety and efficacy evaluation in a first-in-man pilot clinical study. J Cosmet Laser Ther, 20(6), 369-379. PMID: 29482481
7. Mateescu, D. M., et al. (2026). GHK-Cu as a Bioactive Metallopeptide and Drug-Delivery Cargo: Coordination Chemistry, Formulation Science, Therapeutic Evidence, and a Translational Roadmap. Pharmaceutics, 18(9). PMID: 42797253
8. Choi, H. R., et al. (2012). Stem cell recovering effect of copper-free GHK in skin. J Pept Sci, 18(11), 685-90. PMID: 23019153
9. Lee, S. H., et al. (2017). Targeting of CXXC5 by a Competing Peptide Stimulates Hair Regrowth and Wound-Induced Hair Neogenesis. J Invest Dermatol, 137(11), 2260-2269. PMID: 28595998
10. Ryu, Y. C., et al. (2023). CXXC5 Mediates DHT-Induced Androgenetic Alopecia via PGD(2). Cells, 12(4). PMID: 36831222
11. ClinicalTrials.gov search for 'PTD-DBM' and 'KY19382', October 3, 2026: no registered studies. ClinicalTrials.gov

Educational information, not medical advice. Each dose in this guide names its source, an approved label or a published study. None is a recommendation for you. An unapproved compound has no established safe or effective human dose, and products sold for “research use only” are not made or tested for people. Talk to a doctor before acting on anything on this site, including before you start, stop or change any medicine or dose.