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# Open the source with the same question in mind.

Here are the papers and records we link to. Each note says what we use it for. There’s no need to read everything: you can open the source behind the claim that brought you here, then see how closely the two match.

## What the hair studies tested

These papers ask different questions. A lotion tested in people, a delivery system tested in mice and a follicle outside the body can’t be rolled into one result. The names matter, too: GHK, GHK-Cu and AHK-Cu aren’t interchangeable.

### [Lee and colleagues — GHK in a combination lotion](https://pmc.ncbi.nlm.nih.gov/articles/PMC4969472/)

A small trial in men with pattern hair loss. Hair counts rose more than with a dummy lotion, but it didn’t test GHK-Cu alone.

### [Liu and colleagues — GHK-Cu delivery in mice](https://pubmed.ncbi.nlm.nih.gov/38026438/)

A system for getting GHK-Cu through mouse skin. Its hair-growth signals don’t establish a treatment for people.

### [Pyo and colleagues — AHK-Cu outside the body](https://pubmed.ncbi.nlm.nih.gov/17703734/)

Human follicles and cells were studied in a lab. The peptide was AHK-Cu, and people weren’t treated.

### [Vickers — an early zinc-thymulin report](https://doi.org/10.4172/2167-0951.1000147)

An open-label pilot in pattern hair loss. This early report can’t establish reliable benefit or long-term safety.

### [Pickart and colleagues — GHK and copper](https://pmc.ncbi.nlm.nih.gov/articles/PMC4508379/)

Background on GHK and its copper-bound form. This review helps explain the names, rather than settle a hair-loss treatment question.

## Safety, approval and getting medical care

These are U.S. records. Dates identify the record we’re describing, rather than an assumed date when FDA changed an ingredient’s status. For a personal treatment question, a licensed clinician is the place to discuss what applies to you.

### [FDA — cosmetic or medicine](https://www.fda.gov/cosmetics/cosmetics-laws-regulations/it-cosmetic-drug-or-both-or-it-soap)

Intended use helps determine the rules. A cosmetic description doesn’t establish a treatment for disease or changes to body function.

### [FDA application records — the prezatide search](https://api.fda.gov/drug/drugsfda.json?search=products.active_ingredients.name:%22PREZATIDE%22)

The search recorded on September 30, 2026 found no approved GHK-Cu medicine. A name in a substance register isn’t approval.

### [FDA — injectable GHK-Cu safety concerns](https://www.fda.gov/drugs/human-drug-compounding/certain-bulk-drug-substances-use-compounding-may-present-significant-safety-risks)

The page current as of April 22, 2026 lists the injectable entry as nominated but withdrawn. Safety concerns remain; withdrawal isn’t clearance.

### [FDA — the separate non-injectable GHK-Cu entry](https://www.fda.gov/media/94155/download)

The May 14, 2026 list places non-injectable GHK-Cu in Category 1. Its temporary policy has conditions and isn’t FDA approval.

### [FDA — what compounding means](https://www.fda.gov/drugs/human-drug-compounding/compounding-and-fda-questions-and-answers)

Medicines prepared for particular patient needs. Compounded medicines aren’t FDA-approved; having a prescription doesn’t change that.

### [State medical boards — finding a licence record](https://www.fsmb.org/contact-a-state-medical-board/)

A directory leading to state medical and osteopathic boards. A licence record is a check, rather than a recommendation of a clinician.

For the explanation around these sources, return to [the overview](/) or read [why we keep the hair concern first](/about).

Hair Loss Peptide is a guide for hair questions, where we explain the reading without providing clinical care, pharmacy services or sales.

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