What it is
GHRP-6 — growth hormone-releasing peptide-6 — is a synthetic hexapeptide: six amino acids, His-D-Trp-Ala-Trp-D-Phe-Lys-NH2, with a molecular weight of 872.44 daltons. Two of its residues are D-amino acids, the mirror-image form of the natural ones, which is a standard way of stopping a short peptide from being broken down immediately.
It makes the pituitary gland release growth hormone. It does this through the receptor that ghrelin uses — and the chronology there is unusual enough to be worth stating. GHRP-6 was developed in the 1980s out of Cyril Bowers's work on growth hormone-releasing peptides. Ghrelin, the body's own signal at that receptor, was not identified until 1999. The drug came first; the hormone it imitates was found more than a decade later.
That heritage explains its most consistently reported effect. The ghrelin receptor is the hunger receptor, and GHRP-6 makes people hungry.
A real human literature, in an empty registry
This entry exists to reconcile two numbers that look contradictory.
PubMed indexed 785 records for GHRP-6 on 2026-09-11, of which 307 carry a human tag — around four in ten. ClinicalTrials.gov held zero registrations.
This library has learned to be suspicious of a high human paper count sitting next to an empty registry: with LL-37 and the mitochondrial peptide MOTS-c, that pattern turned out to mean the research measures the body's own molecule rather than administering anything. That is not what is happening here. GHRP-6's human papers are genuine administration studies — volunteers and patients given the peptide, with hormone responses measured afterwards.
The empty registry has a duller explanation: a date. ClinicalTrials.gov opened in 2000, and registration became a precondition of publication in major journals only from around 2005. GHRP-6's human programme ran largely through the 1990s, in academic endocrinology departments, and was published in journals like the Journal of Clinical Endocrinology and Metabolism, Clinical Endocrinology and The Lancet without ever touching a registry. An empty registry means "studied before registries existed" here, not "never studied".
It is the only compound in this library so far where the absence of registrations is a fact about the calendar rather than about the compound.
What the human studies measured
Almost entirely one thing: what the pituitary does in the minutes and hours after a dose.
The best-characterised piece is the pharmacokinetics. A 2013 study in the European Journal of Pharmaceutical Sciences (2013;48(1-2):40-6), run at the Center for Genetic Engineering and Biotechnology in Havana, gave nine healthy male volunteers single intravenous bolus doses of 100, 200 and 400 micrograms per kilogram and quantified the peptide in plasma by mass spectrometry:
| Measure | Result |
|---|---|
| Distribution half-life | 7.6 ± 1.9 minutes |
| Elimination half-life | 2.5 ± 1.1 hours |
| Dose proportionality | Area under the curve increased roughly in proportion to dose |
| Unexplained finding | Atypical concentration spikes during elimination in 4 of 9 subjects |
That last row is the part worth keeping. The authors report it plainly and do not explain it: nearly half of a nine-person cohort showed plasma behaviour the model did not predict. Nine subjects is too few to interpret it, but it is exactly the kind of detail that vanishes when a half-life gets quoted second-hand.
The rest of the human record is provocation testing and comparative endocrinology — how the response compares with ghrelin's, how it changes in thyrotoxicosis, whether it needs the body's own growth hormone-releasing hormone to work. A 2000 paper in The Lancet examined GHRP-6 and GHRH together as a diagnostic test for growth hormone deficiency in adults.
That is the closest this compound came to a clinical role: not a treatment, a test.
What was never measured
Nothing in the registry, and nothing this library found in the human literature, tests GHRP-6 for muscle mass, strength, body composition, recovery or sleep quality.
The human work establishes that a dose produces a pulse of growth hormone. The claims made for it concern what months of those pulses do to a body. Those are different questions, and the second one has not been asked in a published human study of this compound.
A caution about the literature while doing this kind of check: a search for GHRP-6 human trials returns a 1998 Journal of Clinical Endocrinology and Metabolism paper on eight months of treatment with graded doses of a growth hormone-releasing peptide in growth hormone-deficient children — a longitudinal study with a growth-velocity outcome, exactly what one would want here. Opening it shows the peptide studied was GHRP-2, not GHRP-6. It is not evidence about this compound, and it is the sort of near-miss that becomes a citation if the abstract is not read.
Where it stands
No approved medicine. DailyMed and Drugs@FDA returned nothing under this name on 2026-09-11. What is sold is a lyophilised research powder.
Related reading
The close chemical relatives: the peptide of identical length approved in Japan as a diagnostic, which shares this one's Trp-D-Phe-Lys tail and its empty registry, its close sibling hexarelin, and — within this library's growth hormone group — ipamorelin, designed later for a cleaner hormone profile, and the compounds sold as CJC-1295, which raise growth hormone by a different route entirely. Sermorelin is the one compound in that group that was once an approved US medicine. The tesamorelin entry covers the one that still is.