GHRP-2 Peptide: Pralmorelin, GH Secretagogue Science and Safety
GHRP-2 (pralmorelin) peptide guide covering ghrelin-receptor biology, the Japan-approved GH-deficiency diagnostic test, dosing context, half-life and safety limits.
GHRP-2 is a peptide that is easy to misread. In research and consumer-market discussions it is often presented as a simple "growth hormone booster," but its documented identity is narrower and more specific. GHRP-2, also called pralmorelin and coded KP-102 or GPA-748, is a synthetic hexapeptide growth hormone secretagogue whose only regulatory approval anywhere is as a single-dose diagnostic agent in Japan.
That distinction matters. A compound approved to provoke a measurable growth hormone pulse during a clinic test is not the same thing as an approved treatment for body composition, aging or recovery. The human evidence behind GHRP-2 is real, but most of it describes what happens in the minutes after a single injection, not what happens after months of repeated self-administration.
This guide is educational and not medical advice. GHRP-2 is not an approved consumer therapeutic in the United States or most of the world. It should not be treated as a wellness protocol, and nothing here is a dosing recommendation.
For broader context, compare this guide with the ghrelin-mimetic family overview through GHRP-6, the more selective ipamorelin, the related hexarelin, and the general explainer on what peptides are.
GHRP-2 At A Glance
| Question | Evidence-aware answer |
|---|---|
| What is it? | A synthetic hexapeptide ghrelin mimetic and growth hormone secretagogue, also called pralmorelin (KP-102, GPA-748). |
| Sequence | D-Ala-D-2-Nal-Ala-Trp-D-Phe-Lys-NH2 (a six-amino-acid peptide). |
| Main target | The growth hormone secretagogue receptor (GHS-R1a), the same receptor activated by ghrelin. |
| Approval status | Approved in Japan only as a single-dose GH-deficiency diagnostic (pralmorelin). Not FDA-approved; research-only elsewhere. |
| Main documented effect | A rapid, transient growth hormone pulse, plus smaller rises in ACTH, cortisol and prolactin. |
| Main safety frame | Off-target pituitary-adrenal and prolactin effects, appetite stimulation, and limited long-term human data. |
How GHRP-2 Triggers Growth Hormone Release
GHRP-2 belongs to a family of small synthetic peptides originally developed in the lineage of work by Bowers and colleagues, before the natural ligand of the target receptor was even known. We now understand that GHRP-2 is a ghrelin mimetic: it activates the growth hormone secretagogue receptor, GHS-R1a, the same receptor that the stomach hormone ghrelin uses.
Mechanistically, GHRP-2 acts at two sites. At the hypothalamus it increases release of growth hormone-releasing hormone (GHRH) and blunts the inhibitory tone of somatostatin. At the pituitary it acts more directly on the somatotroph cells that store and release growth hormone. The combined effect is a sharp, pulse-like release of growth hormone rather than a flat, continuous elevation. General pharmacology work on KP-102 in multiple animal species described it as a potent GH releaser acting at both hypothalamic and pituitary sites, with negligible effects on respiratory, cardiovascular, digestive and renal systems at tested doses.
This two-site, pulse-driven mechanism is why secretagogues are often contrasted with injecting growth hormone itself. The body's own feedback loops still apply, and the pituitary still has to have functioning somatotrophs to respond, which is exactly what makes GHRP-2 useful as a diagnostic probe. For more on the GHRH side of this axis, see sermorelin and CJC-1295, which work through the GHRH receptor rather than the ghrelin receptor.
What The Human Evidence Actually Shows
The strongest, cleanest GHRP-2 evidence is diagnostic. In a Journal of the Endocrine Society study, a 100-microgram intravenous bolus of GHRP-2 was used to evaluate hypothalamic-pituitary disorders, with peak growth hormone responses used to classify severe, moderate and non-deficient categories. Pediatric work used a weight-based intravenous dose of roughly 2 micrograms per kilogram, where peak growth hormone was markedly lower in children with deficiency (median near 3.4 micrograms per liter) than in those without (median near 25 micrograms per liter). Adult testing has used growth hormone cut-offs around 15 micrograms per liter to identify severe deficiency, often comparing GHRP-2 to insulin tolerance testing.
A second, well-documented effect is on appetite. In a randomized study in lean healthy men, a subcutaneous GHRP-2 infusion increased food intake by roughly 36 percent compared with saline, mirroring ghrelin's known appetite effect. A separate study found obese subjects also increased food intake in a dose-dependent way, and a long-term oral GHRP-2 study in growth-hormone-deficient children reported increased appetite in most treated patients. This is a predictable consequence of activating the ghrelin receptor, and it is a feature, not a footnote, of any honest GHRP-2 discussion.
The third documented effect is on the pituitary-adrenal axis. Research in patients with hypothalamopituitary disorders showed GHRP-2 can directly stimulate ACTH release, and the GHRP-2 test has been studied as a screen for secondary adrenal insufficiency, with cortisol and ACTH response cut-offs reported alongside the growth hormone readout.
What the human evidence does not establish is a validated therapeutic role. There is no approved indication for GHRP-2 as a treatment for muscle gain, fat loss, anti-aging or athletic recovery. The development program that explored GHRP-2 for growth hormone deficiency and short stature did not result in an approved treatment for those conditions, and the only marketed product is the Japanese diagnostic. Claims that lean on the diagnostic data to imply proven long-term therapeutic benefit are overstating the record.
Dosing Context (Not A Recommendation)
The only dosing figures with primary-source support describe the diagnostic test, not a treatment regimen. They are listed here for context only.
| Setting | Reference figure from the literature | Important limit |
|---|---|---|
| Adult diagnostic test | A single 100-microgram intravenous bolus, with growth hormone sampled over about an hour. | This is a one-time provocative test, not a repeated therapeutic dose. |
| Pediatric diagnostic test | Roughly 2 micrograms per kilogram intravenously. | Pediatric testing is done under specialist supervision in a clinical setting. |
| Oral administration | Studied historically, but oral activity is a tiny fraction of intravenous activity. | Oral bioavailability is very low; the approved product is parenteral. |
Because the approved use is a single injection, there is no established, evidence-based chronic dose, frequency or duration for GHRP-2. Any repeated self-dosing protocol circulating in consumer channels is extrapolation, not a validated regimen.
Pharmacokinetics And Half-Life
GHRP-2 acts quickly and clears quickly. In diagnostic use, growth hormone rises within about 15 to 60 minutes of an intravenous dose and typically returns toward baseline within a few hours. The peptide itself has a short circulating presence consistent with a rapid-acting secretagogue rather than a long-acting depot. Because precise human half-life values vary by route and assay and are not consistently reported in the primary diagnostic literature, this guide does not assign a single exact number; the practical point is that GHRP-2 produces a brief, transient pulse, not sustained exposure. For why this matters across the whole secretagogue class, see the peptide half-life explainer.
Safety Considerations
GHRP-2's safety questions follow directly from its mechanism. Because it activates the ghrelin receptor broadly, its effects are not limited to growth hormone.
| Safety issue | Why it matters |
|---|---|
| Cortisol and ACTH elevation | GHRP-2 can directly stimulate ACTH and raise cortisol, which is undesirable for repeated use outside a controlled test. |
| Prolactin elevation | Like related GHRPs, GHRP-2 can raise prolactin, an off-target endocrine effect. |
| Appetite stimulation | Ghrelin-receptor activation reliably increases hunger and food intake in human studies. |
| Limited long-term data | The compound was validated as a one-time diagnostic, so chronic-use safety in healthy people is not well characterized. |
| Source and purity risk | Research-market material is unregulated, so identity, sterility and dosing accuracy are not assured. |
| Pituitary-axis interactions | Effects on the GH and adrenal axes mean results and risks depend on a person's underlying endocrine status. |
General pharmacology testing in animals reported a reassuring profile for a single diagnostic dose, with minimal cardiovascular, respiratory, digestive and renal effects. That is meaningful for the approved use case. It does not answer the different question of what repeated, unmonitored dosing does over months, which is the scenario most consumer interest actually involves. For a broader look at the category's risks, see growth hormone peptide side effects.
How To Evaluate A GHRP-2 Claim
Use a few filters before trusting any GHRP-2 claim.
First, does the source separate diagnostic evidence from therapeutic claims? A single-bolus test result does not validate a months-long protocol.
Second, does it mention the off-target effects, ACTH, cortisol, prolactin and appetite? A source that only talks about growth hormone is giving you half the pharmacology.
Third, does it acknowledge the approval status honestly? GHRP-2 is an approved diagnostic in Japan and research-only elsewhere. A source implying it is an approved treatment is wrong.
Fourth, is it comparing GHRP-2 fairly to alternatives? Compared with ipamorelin, GHRP-2 tends to drive a stronger GH pulse but with more cortisol, prolactin and appetite effect; compared with hexarelin, it sits within the same potent-but-less-selective end of the family. Selectivity, not just potency, is the relevant axis.
Bottom Line
GHRP-2, or pralmorelin, is a genuine and well-studied growth hormone secretagogue with a clear, narrow evidence base. It reliably provokes a growth hormone pulse by activating the ghrelin receptor at the hypothalamus and pituitary, and that property earned it regulatory approval in Japan as a single-dose diagnostic for growth hormone deficiency.
The same evidence base sets the limits. GHRP-2 is not FDA-approved, has no validated therapeutic indication, raises cortisol, ACTH, prolactin and appetite as off-target effects, and lacks robust long-term human safety data for chronic use. It is best understood as a diagnostic probe and research compound, not as a proven consumer treatment, and any protocol claiming otherwise is extending well beyond what the primary literature supports.
References
Furuta S, et al. General pharmacology of KP-102 (GHRP-2), a potent growth hormone-releasing peptide. Arzneimittelforschung. 2004.
Suzuki S, et al. Clinical Usefulness of the Growth Hormone-Releasing Peptide-2 Test for Hypothalamic-Pituitary Disorder. Journal of the Endocrine Society. 2022.
Yuasa T, et al. Concordant and discordant ACTH responses induced by GHRP-2, CRH and insulin-induced hypoglycemia: evidence for direct ACTH releasing activity of GHRP-2. 2010.
Bowers CY, et al. The growth hormone-releasing activity of a synthetic hexapeptide in normal men and short statured children after oral administration. J Clin Endocrinol Metab. 1992.
Laferrere B, et al. Growth hormone releasing peptide-2 (GHRP-2), like ghrelin, increases food intake in healthy men. J Clin Endocrinol Metab. 2005.
Laferrere B, et al. Obese subjects respond to the stimulatory effect of the ghrelin agonist growth hormone-releasing peptide-2 on food intake. Obesity (Silver Spring). 2006.
Mericq V, et al. Changes in appetite and body weight in response to long-term oral administration of the ghrelin agonist GHRP-2 in growth hormone deficient children. 2003.
Chanson P, et al. Diagnosis and testing for growth hormone deficiency across the ages: accuracy, caveats, and cut-offs for diagnosis. Endocrine Connections. 2023.