What GHRP-2 is
GHRP-2 is a synthetic hexapeptide, also known as KP-102, developed as a growth hormone secretagogue. Researchers at Tulane University, working with the German firm Polygen, produced it from a series of enkephalin-derived analogues screened for pituitary activity. It binds the growth hormone secretagogue receptor, GHS-R1a, the same receptor ghrelin activates.
Japan's Pharmaceuticals and Medical Devices Agency approved GHRP-2 in October 2004 under the generic name pralmorelin, marketed as GHRP Kaken by Kaken Pharmaceutical, for one narrow purpose: diagnosing growth hormone deficiency in adults and children over four years old (Pralmorelin, Drugs in R&D, 5(4):236, 2004). A single intravenous dose reliably separates healthy subjects, whose GH response climbs above 15 mcg/L, from patients with severe GH deficiency, who stay below that threshold. That diagnostic clearance remains the only regulatory approval any GHRP has received anywhere. No agency, including the FDA, has approved GHRP-2 for treatment of any condition, and it is not sold for human use outside Japan's diagnostic context.
Mechanism: how GHRP-2 triggers a GH pulse
GHS-R1a is a G-protein coupled receptor expressed on pituitary somatotrophs and in the hypothalamic arcuate nucleus. Bowers described GHRP-2 and its related hexapeptides years before anyone knew what natural hormone activated GHS-R1a. That gap closed in 1999, when Kojima and colleagues purified a 28-amino acid acylated peptide from rat stomach extracts and showed it activated the same receptor with high potency (Kojima et al., Nature, 402:656, 1999).
They named it ghrelin. GHRP-2 is a synthetic ghrelin mimetic rather than a structural analogue: the two molecules share a binding site, not a backbone.
The GHRH receptor raises cyclic AMP through Gs-protein coupling. GHS-R1a instead couples to Gq and signals through phospholipase C, raising intracellular calcium in the somatotroph. Because the two receptors converge on the same cell through separate pathways, combining a GHRH agonist with GHRP-2 produces more GH output than either compound gives alone.
How much of GHRP-2's effect depends on intact GHRH signaling has its own dedicated literature. Alba and colleagues treated GHRH-knockout mice, which have pituitary hypoplasia and dwarfism from birth, with GHRP-2 at 10 mcg subcutaneously twice a day for six weeks (Alba et al., Am J Physiol Endocrinol Metab, 2005). Chronic GHRP-2 failed to stimulate somatotroph proliferation, failed to raise GH secretion, and failed to promote longitudinal growth in these mice. The result draws a clear line: GHRP-2 acts through a receptor distinct from GHRH, but a functioning GHRH axis is still what the pituitary needs for GHRP-2 to produce a meaningful GH response in vivo.
GHRP-2 also clears the body quickly. Pihoker and colleagues gave ten prepubertal children a single 1 mcg/kg intravenous dose and sampled plasma over two hours (Pihoker et al., J Clin Endocrinol Metab, 83(4):1168, 1998). The disposition fit a two-compartment model with a terminal half-life of 0.55 ± 0.14 hours, about 33 minutes, and a plasma clearance of 0.66 ± 0.32 L per hour per kg. That short half-life is one reason research protocols using GHRP-2 rely on repeated dosing or continuous infusion rather than a single daily injection to sustain receptor activation.
What the human trial data shows
Mericq and colleagues ran the longest published pediatric trial, treating six prepubertal children with growth hormone deficiency for eight months with subcutaneous GHRP-2 at stepwise doses of 0.3, 1.0, and 3.0 mcg per kg per day (Mericq et al., J Clin Endocrinol Metab, 83(7):2355, 1998). Overnight GH secretion rose with each dose increase, and growth velocity during treatment exceeded both the pre-treatment and post-treatment periods. In the final two months, the researchers added GHRH to the GHRP-2 dose and recorded a further rise in GH output, consistent with the receptor synergy described above.
In adults, Wideman and colleagues tested a GHRP-2 bolus combined with intravenous L-arginine, a long-established GH secretagogue, in nine men and nine women in the early follicular phase (Wideman et al., Am J Physiol Regul Integr Comp Physiol, 279(4):R1467, 2000). A 1 mcg/kg GHRP-2 bolus combined with 30 g of arginine over 30 minutes produced a larger GH response than either agent alone, though the size of the synergy differed by sex and was reduced immediately after exercise.
Because GHRP-2 activates the same receptor as ghrelin, it also affects appetite, independent of its GH effect. Laferrere and colleagues infused seven lean, healthy men with GHRP-2 at 1 mcg/kg per hour subcutaneously for 270 minutes, then measured intake at a buffet-style meal; the men ate 35.9 percent more, plus or minus 10.9 percentage points, than they did after a saline infusion (Laferrere et al., J Clin Endocrinol Metab, 90(2):611, 2005). A follow-up trial in 19 subjects, 10 lean and 9 obese, found the appetite effect held in both groups and scaled with dose, from 0.1 to 1 mcg/kg per hour (Laferrere et al., Obesity, 14(6):1056, 2006).
Practical handling for research protocols
GHRP-2 ships as a lyophilized powder and follows the reconstitution and storage rules common to short synthetic peptides. Reconstitute with bacteriostatic water per the reconstitution guide, then refrigerate or freeze the solution promptly, since dissolved peptide degrades faster than the freeze-dried form. Indonesia's climate adds a variable that does not come up in temperate-country protocols: ambient heat and humidity in Bali, Jakarta, and other tier-1 cities accelerate degradation in any reconstituted vial left outside a refrigerator, a point covered at length in the lyophilized peptide storage guide.
Converting between mass, concentration, and injection volume for a given research protocol is easier with the dosing calculator, which handles the arithmetic once a reconstitution concentration is set.
GHRP-2 against the other GH secretagogues
GHRP-2 sits in the same hexapeptide family as GHRP-6 and hexarelin, all developed out of the same Tulane research program and sharing the same GHS-R1a mechanism (see the GHRP-6 research overview). GHRP-2 is generally reported as more potent per microgram than GHRP-6 for GH release, though direct head-to-head human trials at matched doses are limited.
Where GHRP-2 differs most from the newer secretagogues is in its hormone side effects. Like GHRP-6 and hexarelin, GHRP-2 raises cortisol and prolactin alongside GH at GH-releasing doses. Ipamorelin, developed later and covered in the CJC-1295 and ipamorelin research overview, was built specifically to avoid that cortisol and ACTH rise. Researchers choosing between the compounds for a study design are effectively choosing between a well-characterized but less selective secretagogue and a newer one with a narrower hormone profile; the tradeoffs of the CJC-1295 and ipamorelin combination are covered separately.
State of the evidence as of mid-2026
GHRP-2's clinical use case, diagnosing GH deficiency in Japan, has stood since 2004 and remains supported by data going back to the original pralmorelin trials. Its research use case, as a tool compound for studying GHS-R1a pharmacology and ghrelin-linked appetite signaling, has a comparable track record spanning three decades, from the original Bowers-era hexapeptide work through the Laferrere appetite studies of the mid-2000s.
What remains open is how much of GHRP-2's pediatric growth data would replicate in a larger, modern trial. The Mericq cohort was six children, and no Phase 3 program has taken GHRP-2 through registration for a growth indication anywhere outside Japan's diagnostic niche.