GHRP-2 (Pralmorelin): Dosing, Uses and What the Evidence Shows
GHRP-2 holds a distinction no other growth hormone releasing peptide can claim: a national regulator approved it. Japan cleared pralmorelin in 2004. The catch, and it is the whole story, is that the approval is for a diagnostic test, not a treatment. GHRP-2 provokes a clean, measurable pulse of growth hormone, which makes it an excellent probe of pituitary function and a poor foundation for the muscle-building claims stacked on top of it.
This guide keeps the two apart: the dose and use that have a regulatory and clinical basis, and the repeated-injection regimens that do not.
What GHRP-2 is
GHRP-2 is a synthetic hexapeptide with the sequence D-Ala-D-2-Nal-Ala-Trp-D-Phe-Lys-NH2. It carries several names, pralmorelin, KP-102 and GPA-748, and it is the second of the classic growth hormone releasing peptides. It was designed after GHRP-6 to be more potent and to trigger less appetite for a given growth hormone response.
Like the rest of the family, GHRP-2 works through the ghrelin receptor, GHS-R1a. That receptor was cloned before its natural ligand was known, and the growth hormone releasing peptides were the synthetic tools that led investigators to it. When ghrelin was identified as the endogenous agonist, GHRP-2 was reclassified, correctly, as a ghrelin mimetic. It sits in the same class as GHRP-6, hexarelin and the orally active MK-677. The wider family is covered in growth hormone peptides.
How it works
GHRP-2 raises growth hormone through a route that does not depend on GHRH. It acts at both the hypothalamus and the pituitary, and part of its effect comes from functionally opposing somatostatin, the hormone that normally brakes growth hormone secretion. Releasing that brake is why the growth hormone releasing peptides produce responses in situations where GHRH alone does little, and why combined GHRH-plus-GHRP testing produces a response several times larger than either agent given alone.
The response is pulsatile and acute. A dose produces a sharp rise in growth hormone that peaks within about 15 to 30 minutes and clears over the following hour or two; the peptide itself has a short circulating half-life on the order of half an hour. This pharmacology is well suited to a single provocative test. It is much less obviously suited to the goal of raising growth hormone in a durable, physiologically useful way, because the same receptor systems that respond to a first dose can desensitize with repeated exposure.
The approved use: growth hormone stimulation testing
The one thing GHRP-2 does that a regulator has reviewed and cleared is diagnose growth hormone deficiency. Pralmorelin was approved by Japan's PMDA in 2004 as a diagnostic agent for growth hormone deficiency in adults and in children over four years of age, marketed by Kaken Pharmaceutical. No other growth hormone secretagogue has cleared review as a medicine anywhere.
The test works because the response separates cleanly. In people with an intact pituitary, GHRP-2 drives a large, reproducible growth hormone rise regardless of sex, age or obesity; in people with growth hormone deficiency, that rise is markedly smaller. Independent groups have validated the GHRP-2 test in the elderly, in adolescents and in the workup of hypothalamic-pituitary disorders, and it is considered relatively safe compared with the insulin tolerance test, which deliberately induces hypoglycemia.
One quirk of the GHRP-2 test is diagnostically useful in its own right: the same injection that releases growth hormone also releases ACTH and therefore cortisol. Clinicians have used the paired response to gather information about the corticotroph axis at the same time. That property is a feature in a test. It is a liability in anything intended for repeated use.
The dose used in humans
- 1 mcg/kg intravenously is the established human dose, given as a single bolus for growth hormone stimulation testing. For an adult that is roughly 100 mcg.
- Growth hormone is sampled at intervals over about 60 to 120 minutes after injection, and the peak value is what the test reads.
- Subcutaneous, intranasal and oral routes are all active, with a dose-related response, but the non-injected routes need substantially more peptide to release the same growth hormone.
Everything beyond that single supervised dose is extrapolation. The repeated regimens circulated for GHRP-2, typically 100 to 300 mcg once to three times a day, take the diagnostic dose and assume that giving it over and over produces a worthwhile outcome. Some studies of continuous or repeated growth hormone releasing peptide administration in adults have raised IGF-1, which is a real biochemical effect. What is missing is controlled data showing that months of GHRP-2 change body fat, lean mass, strength or any functional endpoint. Its close relative hexarelin was taken to sixteen weeks and produced no measurable change in body fat, lean mass, bone density or IGF-1, which is the most relevant long-run data point the family has.
For the mechanics of handling doses at the microgram scale, see reconstitution, the peptide calculator, and storage.
Appetite: less than GHRP-6, not none
GHRP-2 is often sold as the growth hormone releasing peptide that spares you the hunger. That is a comparison, not an absolute. GHRP-2 activates the ghrelin receptor, and ghrelin is the body's principal hunger signal, so an increase in appetite is the expected pharmacology, and GHRP-2 has been studied precisely for its ability to raise food intake.
What is true is that at a growth-hormone-equivalent dose GHRP-2 tends to drive less eating than GHRP-6, which is the hungriest member of the class. If appetite is unwanted, the cleaner choice is ipamorelin, which was designed to release growth hormone with minimal ghrelin-like side effects.
Selectivity: the cortisol and prolactin problem
The growth hormone releasing peptides do not release growth hormone in isolation. GHRP-2 raises ACTH and cortisol, and to a smaller extent prolactin. In a one-off diagnostic test that is harmless and sometimes useful. As a repeated intervention it is the reason the older peptides were superseded in most settings by more selective compounds.
This is the exact gap ipamorelin was built to close: a ghrelin receptor agonist that triggers the growth hormone pulse without meaningfully moving cortisol or prolactin. If the goal is a growth hormone pulse and nothing else, GHRP-2 is not the selective option, and any page implying it is has skipped the endocrine literature. Compare the family directly in GHRP-2 vs GHRP-6 and ipamorelin vs GHRP-2.
Why GHRP-2 gets paired with a GHRH analogue
GHRP-2 and the GHRH analogues act on different receptors and are synergistic. Given together they release far more growth hormone than either alone, which is the pharmacological basis of the combined diagnostic test and of the stacked protocols marketed for physique goals. The GHRH-receptor side of that pairing includes sermorelin, CJC-1295 and tesamorelin.
The synergy is real. What it demonstrates is a larger growth hormone spike, measured in a lab. It does not, on its own, demonstrate that the combination produces the body-composition results attached to it in marketing. The most common stack pairs a GHRH analogue with a GHRP; see CJC-1295 with ipamorelin and how these compounds are positioned in peptides used in bodybuilding.
Safety, legality and supply
A single supervised GHRP-2 test dose has a good tolerability record, which is unsurprising for one injection given under observation. There is little human safety data for repeated GHRP-2 use over months or years, because the studies that would generate it were never run. The generic concerns that come with pushing growth hormone and IGF-1, for insulin sensitivity and for anyone with an active or suspected cancer, have not been resolved for this compound.
Outside Japan's diagnostic approval, GHRP-2 is not an approved medicine and is sold as a research chemical, so it may not lawfully be marketed for human consumption and no regulator has checked the purity, sterility or labeling accuracy of any vial on sale. See legal status of research peptides and FDA-approved peptides for what has actually cleared review.
GHRP-2 is prohibited at all times under section S2 of the WADA Prohibited List, and anti-doping laboratories can detect it and its metabolites, including from dried blood spot samples. Peptides versus steroids covers the anti-doping picture, and general class effects are in peptide side effects. For technique, see how to inject peptides and injection sites.
The bottom line
GHRP-2 is the growth hormone releasing peptide that actually reached approval, and the approval tells you what it is good at: producing a clean, reproducible growth hormone pulse that a clinician can measure. As a diagnostic it is genuinely useful. As a treatment it rests on the same thin foundation as the rest of the family, a well-documented acute effect and an almost empty file of long-term outcome data, plus a cortisol and prolactin rise that more selective peptides avoid.
If the interest is a growth hormone pulse without the spillover, ipamorelin is the more sensible member of the class. If the interest is what GHRP-2 can prove, the answer is pituitary function, at 1 mcg/kg, once.
Frequently Asked Questions About GHRP-2
GHRP-2 is a synthetic hexapeptide, D-Ala-D-2-Nal-Ala-Trp-D-Phe-Lys-NH2, also called pralmorelin, KP-102 and GPA-748. It is a growth hormone secretagogue: it binds the ghrelin receptor (GHS-R1a) and triggers a pulse of growth hormone release from the pituitary through a pathway separate from GHRH. It is the second of the classic growth hormone releasing peptides, developed after GHRP-6 and designed to be more potent and more selective.
The dose with an actual regulatory and clinical basis is 1 mcg/kg intravenously, roughly 100 mcg for an average adult, given as a single bolus for growth hormone stimulation testing. That is the approved diagnostic dose in Japan. The higher, repeated subcutaneous doses discussed in peptide circles, commonly 100 to 300 mcg once to three times daily, are extrapolations from that single test dose. They are not a validated treatment regimen and no outcome-based dose-ranging trial supports them.
No. GHRP-2 is not approved by the FDA for any use. It is, however, approved in Japan, where pralmorelin was cleared by the PMDA in 2004 as a diagnostic agent for growth hormone deficiency in adults and children over four. That makes GHRP-2 the only growth hormone secretagogue ever approved by any national regulator, and the approval is for a test, not a therapy. In the United States it is sold only as a research chemical.
Yes, though less than GHRP-6. GHRP-2 is a ghrelin receptor agonist, and ghrelin is the hunger hormone, so appetite stimulation is expected and is documented. GHRP-2 has been studied specifically for its ability to increase food intake. The common claim that GHRP-2 does not cause hunger is wrong; the accurate statement is that it is less orexigenic than GHRP-6, not that it is appetite-neutral.
Diagnosis. The GHRP-2 stimulation test is a reliable, reproducible way to provoke growth hormone release and separate people with growth hormone deficiency from those without, because the response is blunted in deficiency. It is used in adults, the elderly and children, and it is relatively safe compared with the insulin tolerance test. What GHRP-2 does not have is an approved therapeutic indication in any country.
Yes. Alongside growth hormone, GHRP-2 stimulates ACTH and cortisol release, and to a lesser degree prolactin. This is a class property of the older growth hormone releasing peptides and is used deliberately in some pituitary testing. It is also the specific problem ipamorelin was engineered to avoid. Anyone told that GHRP-2 is a clean, selective growth hormone releaser is being told something the endocrine data does not support.
All three act on the same ghrelin receptor. GHRP-6 is the original and the most orexigenic. GHRP-2 is more potent per microgram than GHRP-6 and less hunger-driving, but still raises cortisol and prolactin. Ipamorelin trades some potency for selectivity, releasing growth hormone without the ACTH, cortisol and prolactin spillover. GHRP-2 is the one that reached regulatory approval, as a diagnostic in Japan.
GHRP-2 is not an approved medicine in the United States and is sold only as a research chemical, which means it cannot lawfully be marketed for human use and carries no guarantee of purity or content. It is prohibited at all times under section S2 of the WADA Prohibited List, and anti-doping laboratories can detect GHRP-2 and its metabolites, including from dried blood spot samples. Any drug-tested athlete using it is doping.