C tier · mixed
A real regulatory approval and validated diagnostic performance data in Japan lift GHRP-2 above the rest of the GHRP class, but nothing in the published record supports the body-composition and anti-ageing uses it is actually sold for, and it carries the same ACTH/cortisol, prolactin and appetite off-target burden as its parent compound.
ghrp-2
GHRP-2 (pralmorelin) is a synthetic hexapeptide ghrelin-receptor (GHS-R1a) agonist that reliably triggers a large, short-lived pulse of endogenous growth hormone in humans. It is approved in Japan as a single-use diagnostic agent for growth hormone deficiency; no controlled trial has established that repeated administration produces durable changes in body composition, strength or health outcomes.
// we supply this one
available as a research reagent
≥ 99% HPLC · lyophilised powder · batch certificate published. Grade C above is our own and is not adjusted because we stock it.
the explanation
GHRP-2 tells the pituitary to release a burst of the body's own growth hormone, and it does that job well enough that Japan approved it as a one-off hospital test for growth hormone deficiency. What is missing is any good evidence that using it repeatedly changes muscle, fat or health — plus it also nudges up stress hormones and appetite.
regulatory status
Approved in Japan as a diagnostic agent only; not approved for therapeutic use in any jurisdiction
Marketed in Japan by Kaken as GHRP Kaken 100 for assessment of growth hormone deficiency — a single-administration diagnostic authorisation, not a treatment approval — while FDA has placed GHRP-2 in Category 2 of nominated bulk drug substances (compounded injectable and nasal products 'may pose risk for immunogenicity due to the potential for aggregation and peptide-related impurities') and WADA prohibits it year-round under S2.2.4.
how it works · proposed mechanism
GHRP-2 is a ghrelin-receptor agonist, and essentially every effect attributed to it — wanted or unwanted — follows from that single receptor.
Ghrelin receptor agonism
GHRP-2 binds GHS-R1a, the same receptor as endogenous acylated ghrelin, on pituitary somatotrophs and hypothalamic neurons. It acts through a pathway distinct from and additive to GHRH, which is why combined GHRH plus GHRP testing produces larger GH peaks than either alone.
Pulse, not plateau
The GH response is a sharp, self-limiting pulse rather than a sustained elevation, and somatostatin tone plus receptor desensitisation blunt repeat responses. This pulsatile profile is precisely what makes it a usable diagnostic stimulus and a poorly characterised chronic agent.
Corticotroph and lactotroph spillover
GHS-R1a is expressed beyond somatotrophs, so the same dose that releases GH also releases ACTH, cortisol and prolactin. In direct comparison the ACTH and cortisol responses to GHRP-2 were of a magnitude comparable to those produced by human CRH itself (Arvat 1997).
Central appetite drive
Arcuate-nucleus GHS-R1a activation is orexigenic, and this reproduces in humans: subcutaneous GHRP-2 infusion increased free-feeding energy intake by roughly a third versus saline in lean men. In GH-deficient children on twelve months of oral GHRP-2, seven of ten reported a significant appetite increase.
what’s reported
evidence shape
6 sourcesThe composition of the cited literature by study type. This describes the shape of the evidence, not its quality — and it does not by itself set the grade.
⚠ the catch
The Japanese approval that people cite as validation is for a single diagnostic injection in a clinic — it says nothing about the repeated self-administration the compound is actually marketed for, and it is not an efficacy finding for muscle, fat or recovery. Meanwhile the same receptor that produces the GH pulse also drives cortisol, prolactin and hunger, and FDA has formally flagged compounded GHRP-2 injectables as an immunogenicity risk.
key published findings
- Human crossover trial (Arvat 1997, Peptides, n=6 young + 6 elderly adults): GH responses to 2 µg/kg IV GHRP-2 exceeded those to GHRH (p<0.05); prolactin responses were significant but lower than TRH (p<0.01), while ACTH and cortisol responses were comparable in magnitude to those elicited by human CRH.
- Human trial (Laferrère 2005, J Clin Endocrinol Metab, n=7 lean men): subcutaneous GHRP-2 infusion increased free-feeding energy intake by 35.9 ± 10.9% versus saline, with intake rising from 101.3 to 136.0 kJ/kg — a directly measured orexigenic effect, not an inference from ghrelin biology.
- Human diagnostic validation (Asakura 2010, J Pediatr Endocrinol Metab, n=56 children): 2 µg/kg IV GHRP-2 correlated with insulin tolerance testing (p<0.0001); median peak GH was 3.39 µg/L in GHD versus 25.10 µg/L in non-GHD children, with a 15 µg/L cut-off giving optimal sensitivity and specificity, and the test completing in one hour or less.
- Human trial, 12 months (Mericq 2003, J Pediatr Endocrinol Metab, n=10 prepubertal GH-deficient children, oral GHRP-2 900 µg/kg twice daily): seven of ten reported significant appetite increase in the first 6 months, but the change in BMI SDS did not reach statistical significance (0.21 ± 1.5 vs 0.25 ± 1.5) — appetite stimulation without a demonstrated durable body-composition effect.
- Regulatory (FDA, Category 2 bulk drug substances): 'Compounded drugs containing GHRP-2 for injectable and nasal administration may pose risk for immunogenicity due to the potential for aggregation and peptide-related impurities.'
limitations of the evidence
- Human pharmacokinetics are poorly characterised in the public literature — no well-replicated elimination half-life for GHRP-2 has been published, in contrast to GHRP-6, so half-life figures circulating in vendor material are unsourced.
- There is no randomised controlled trial of repeated GHRP-2 administration with body composition, strength, or clinical outcome as a primary endpoint in healthy adults; the entire human record is acute diagnostic testing plus small paediatric and critical-illness studies.
- Tachyphylaxis is expected on pharmacological grounds from a GPCR agonist given repeatedly, but the degree and time course of GH-response attenuation with chronic dosing has not been quantified in humans.
documented safety signals
- Dose-dependent ACTH and cortisol release comparable in magnitude to human CRH stimulation (Arvat 1997) — an HPA-axis activation that is unwanted in any non-diagnostic context.
- Significant prolactin elevation in the same acute human studies.
- Reproducible orexigenic effect (+35.9% energy intake) that works directly against the body-composition goals for which the compound is typically marketed.
- FDA Category 2 designation for immunogenicity risk in compounded injectable and nasal preparations arising from aggregation and peptide-related impurities.
- GH secretagogues raise IGF-1 and can worsen insulin sensitivity as a class effect; chronic dysglycaemia risk is flagged in the 2026 Frontiers in Endocrinology review of self-administered GH-axis peptides but is not quantified for GHRP-2 specifically.
identity
| full name | Growth Hormone-Releasing Peptide-2 (pralmorelin) |
| category | Growth Hormone |
| modality | peptide |
| formula | C45H55N9O6 |
| molar mass | 817.98 g/mol |
| cas | 158861-67-7 |
| sequence | D-Ala-D-2-Nal-Ala-Trp-D-Phe-Lys-NH2 (C-terminally amidated) |
laboratory handling
| storage | Lyophilised powder is stored at -20 °C, desiccated and protected from light, and is generally stable for short shipping periods at ambient temperature; once reconstituted, aqueous solutions are held at 2-8 °C for short-term laboratory use or aliquoted and frozen at -20 °C to avoid repeated freeze-thaw cycles. |
| solubility | Readily soluble in sterile or bacteriostatic water and in aqueous buffers at neutral pH; laboratory stock solutions are also prepared in dilute acetic acid or DMSO where higher concentrations are required. |
| co-studied with | In research settings GHRP-class peptides are routinely paired with a GHRH analogue because the two act through separate receptors and produce a larger combined GH pulse than either alone — a pharmacological observation from acute testing, not a demonstrated outcome benefit. |
Handling information describes laboratory practice for a research reagent. It is not a preparation guide for use in humans.
the receipts
6 citedU.S. Food and Drug Administration · 2023 · official
NCATS Inxight Drugs, National Center for Advancing Translational Sciences · 2024 · official
Peptides · 1997 · peer-reviewed
The Journal of Clinical Endocrinology & Metabolism · 2005 · peer-reviewed
Journal of Pediatric Endocrinology & Metabolism · 2010 · peer-reviewed
Journal of Pediatric Endocrinology & Metabolism · 2003 · peer-reviewed
others in Growth Hormone