GHRP-6 returns zero registered clinical trials. It also has a complete human pharmacokinetic study with a validated mass-spectrometry assay, an internal standard and a two-compartment model.
Both statements are true, and reconciling them is the most useful thing on this page — because this site made almost exactly the same discovery about GHRP-2 a day earlier, on a different continent.
The registry says nothing, again
ClinicalTrials.gov, 21 September 2026: 0 studies for GHRP-6.
Yesterday's GHRP-2 record established the reading rule that applies here. A registry census is a census of that registry, and a zero from it means the compound is absent from that registry and nothing more. For GHRP-2 the missing literature was Japanese. For GHRP-6 it is Cuban.
The Center for Genetic Engineering and Biotechnology in Havana — CIGB — developed and studied this peptide, and its work appears in European journals without ever passing through a US registry.
This is now the second consecutive compound where a registry zero would have produced a false claim. It should stop being treated as a surprise on this site and start being treated as a step: before a zero is written down as an absence, ask where that compound's studies would have been filed.
The pharmacokinetic study, which most pages on this compound do not know exists
Cabrales et al., Eur J Pharm Sci 2013;48(1–2):40–6 (PMID 23099431) — Pharmacokinetic study of Growth Hormone-Releasing Peptide 6 (GHRP-6) in nine male healthy volunteers.
| Subjects | 9 male healthy volunteers |
|---|---|
| Doses | 100, 200 and 400 μg/kg body weight |
| Route | Single intravenous bolus |
| Assay | Validated LC-MS, 13C3Ala-GHRP-6 internal standard, LLOQ 5 ng/mL |
| Distribution half-life | 7.6 ± 1.9 min |
| Elimination half-life | 2.5 ± 1.1 h |
| Model | Two-compartment, R² > 0.99 |
Three details raise this above the usual standard of a research-compound source.
The assay was developed and validated separately and published first, following FDA guidance, with a stable-isotope internal standard — which is the difference between a concentration and a number.
The lower limit of quantification was reached in all nine subjects at 12 hours, capturing over 85% of the area under the curve, so the half-life is modelled on most of the curve rather than extrapolated from its beginning.
And the paper reports an anomaly it could not account for: atypical concentration spikes during the elimination phase in four of the nine subjects. A study that prints the four subjects who did not behave is a more trustworthy study than one that does not, and the spikes are a real limitation on the elimination figure.
Two human dose records, and they are not versions of each other
| Diagnostic | Pharmacokinetic | |
|---|---|---|
| Dose | 93 μg total | 100–400 μg/kg |
| For an 80 kg adult | 93 μg | 8,000–32,000 μg |
| Given with | GHRH 100 μg, same bolus | Nothing |
| Route | Intravenous bolus | Intravenous bolus |
| Purpose | Provoke a GH response to measure it | Trace the molecule to model a curve |
| Population | 10 elderly men, 9 severely obese men, 7 controls | 9 healthy men |
| Source | Eur J Endocrinol 2005;152(4):575–80 | Eur J Pharm Sci 2013;48(1–2):40–6 |
Roughly 250-fold apart, and neither figure means anything in the other's setting. The diagnostic dose is sized to move one hormone above or below a threshold once. The pharmacokinetic dose is sized to keep plasma concentrations above an assay's detection floor long enough to fit a model.
Neither study asked what happens when the compound is given repeatedly to a healthy adult, which is what it is sold for.
The 93 μg figure is also worth pausing on because it is odd — not a round number, and given with 100 μg of GHRH in the same injection. It is a combined test, designed to interrogate two signalling routes to the pituitary at once, and the GHRP-6 half of it is not a standalone dose.
The diagnostic test failed in one of the groups it was tested on
Haijma and colleagues set out to check whether the accepted cut-off — a peak growth hormone of 15 μg/L after the combined GHRH/GHRP-6 test — held in elderly and severely obese men.
| Group | n | Peak GH | AUC (μg/L × 120 min) |
|---|---|---|---|
| Severely obese men (mean BMI 40.6) | 9 | 13.2 μg/L | 707 |
| Elderly men (mean age 74) | 10 | 35.0 μg/L | 2,274 |
| Healthy controls | 7 | 53.4 μg/L | 3,250 |
Peak GH stayed below the 15 μg/L threshold in seven of the nine severely obese men, and the authors concluded the cut-off cannot be used in that group. Body composition moved the result far enough to make a validated diagnostic threshold produce the wrong answer.
That is a finding about the test, not about the compound — and it is directly relevant to anyone reading a GHRP-6 growth-hormone response figure, because the size of the response depends heavily on who received it.
A paper that reads clinical and is not
Cibrián et al., Clin Sci (Lond) 2006;110(5):563–73 (PMID 16417467) is titled Use of growth-hormone-releasing peptide-6 (GHRP-6) for the prevention of multiple organ failure, and it is cited widely as evidence for this compound's tissue-protective effects.
Read the methods and it is entirely preclinical: rat intestinal epithelial (IEC-6) and human colonic cancer (HT29) cell lines for the migration work, and a rat model of hepatic vessel ischaemia and reperfusion for the in vivo work. The dose in it — 120 μg/kg intraperitoneally — was given to rats. The paper's own conclusion says further studies appear justified.
The title is not misleading in a journal, where the readership supplies the context. It is misleading once the citation travels, and a dose figure lifted from it lands in a human dosage discussion carrying a rat's route of administration.
Detection, and the one-volunteer nasal study
GHRP-6 is on the World Anti-Doping Agency Prohibited List, and the analytical literature is where several of the most concrete human administration records live.
Semenistaya et al., Drug Test Anal 2015;7(10):919–25 (PMID 25869809), from the Moscow Anti-Doping Centre with the German Sport University Cologne, administered GHRP-1, GHRP-2, GHRP-6, hexarelin and ipamorelin nasally, one volunteer per compound, and collected urine for two days to characterise metabolites by nano-LC high-resolution mass spectrometry.
One volunteer per compound is not a dose study and is not offered as one. It is worth recording for two reasons: it is a human administration by a route almost nothing else in this record uses, and it is a reminder that a large share of what is known about how these peptides behave in people was learned by laboratories trying to catch them.
A citation trap this catalogue has already been caught by
PMID 9661608 is a GHRP-2 trial. It is not a GHRP-6 trial.
It is the eight-month dose-escalation study in six growth hormone-deficient children, and it is routinely attributed to GHRP-6 in citation lists. This site's compound library caught the misattribution on 11 September 2026 and the GHRP-2 dosage record states it. A dose figure copied from a list that names the wrong compound does not change any digits, which is precisely why it survives.
Method
The ClinicalTrials.gov v2 API was queried on 21 September 2026 for GHRP-6. Literature was searched on PubMed the same day; every abstract cited above was opened and read rather than taken from a result list, which is this site's standing rule after a near-miss on 20 September. Doses are quoted with the unit, route and population the source states. Where a paper's dose was administered to animals or to cells, that is said in the same sentence as the figure. Related records: the dosage chart grades every compound here by the tier of source behind its figure, the half-life chart carries the 7.6-minute and 2.5-hour figures with their route attached, and how to read a dosing claim sets out why a per-kilogram research dose and a fixed diagnostic dose are not the same kind of number. Nothing on this page is a dosing instruction.