Evidence on peptides for uneven pigmentation is product- and sequence-specific. A small randomized split-face study tested one cream containing PTPD-12. That result does not establish that nonapeptide-1 (melanostatin), GHK-Cu, or peptide products generally reduce dark spots by a stated percentage.
What a human peptide study tested
| Study | Design and measure | Reported result | Scope |
|---|---|---|---|
| PTPD-12 cream, randomized split-face trial | 21 participants with facial hyperpigmentation; one side received a PTPD-12 cream and the other a control cream twice daily for eight weeks. Researchers measured melanin index and clinical assessments. | Mean melanin index on the treated side decreased from 216.93 to 194.69 at week eight. | A small study of one formulation and peptide. It did not test melanostatin or GHK-Cu, and the within-side change is not a universal treatment effect. |
Claims the reviewed sources do not support
The sources reviewed for this article do not substantiate the former claims that melanostatin reduces melanin by 37% in eight weeks, GHK-Cu accelerates skin renewal by 42%, named peptides reduce pigmentation by 25% to 40%, or results follow a standard 4-to-6-week timeline. The prior source list did not match those specific percentages or treatment claims, so the numbers and mismatched references have been removed.
How to interpret peptide-pigmentation research
Match the exact peptide and formulation to the study, then check whether the evidence comes from people, cells, skin models, or animals. A measured melanin-index change in a small split-face study does not establish the same result for every dark spot, diagnosis, concentration, or commercial product.
Check your GLP-1 eligibility
Use our free BMI Calculator to see if you may qualify for provider-reviewed GLP-1 therapy.
Try the BMI Calculator →Other pigmentation studies are not automatically peptide evidence
A 2025 trial evaluated a 2-mercaptonicotinoyl glycine serum against hydroquinone for melasma. That ingredient is not one of the peptides compared above, so its results should not be attributed to peptide products.
FAQ
Does melanostatin reduce dark spots by 37%?
The reviewed sources did not substantiate that figure. The human study identified for this page tested PTPD-12, a different peptide.
Has GHK-Cu been shown to reduce hyperpigmentation by 42%?
The sources reviewed here did not substantiate that percentage as a human hyperpigmentation outcome.
What did the PTPD-12 study measure?
It measured melanin index and clinical assessments over eight weeks in 21 participants using a specific cream in a split-face design.
Human studies
- Efficacy and Safety of a PTPD-12-Containing Cream on Improvement in Hyperpigmentation: A Randomized, Split-Face Clinical Trial.
- Randomized study of 2-mercaptonicotinoyl glycine serum versus hydroquinone for melasma, 2025. The ingredient is not a peptide.
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