GHRP-2

GHRP-2 (also called pralmorelin) is a synthetic six-amino-acid peptide that triggers the body to release its own growth hormone by activating the ghrelin receptor. It was developed in the 1980s-1990s as a growth-hormone-releasing tool and is approved in Japan as a diagnostic injection used to test whether a patient’s pituitary gland can release growth hormone normally. It is not approved anywhere as a treatment peptide, and most of what circulates about it online — dosing charts, stacking advice, fat-loss claims — comes from research-chemical vendors and bodybuilding communities rather than clinical medicine.

Research snapshot

Peptide category	Synthetic growth hormone releasing hexapeptide (ghrelin receptor agonist)
Primary research interest	Diagnostic use (evaluating growth hormone deficiency) in its approved Japanese indication; growth hormone release generally in off-label use
Highest available evidence	Tier 1/2 for its approved Japanese diagnostic indication; community/vendor evidence only for off-label therapeutic-style use
Human research available	Yes for its approved diagnostic use in Japan; not developed through modern trials for a general therapeutic indication
Development status	Approved in Japan as a diagnostic agent; not developed further into a general therapeutic product elsewhere
Regulatory status	Approved in Japan (marketed by Kaken Pharmaceutical as GHRP Kaken 100, a diagnostic agent); not approved by the FDA or EMA for any indication; not legally marketed in the US as a drug or supplement

Technical identity

Primary name	GHRP-2 (pralmorelin)
Alternative names	Pralmorelin; KP-102; marketed in Japan as GHRP Kaken 100
Peptide sequence	Not independently re-verified in this pass — a six-amino-acid sequence including non-standard building blocks
Amino-acid length	6 (hexapeptide, includes non-standard amino acids)
Molecular formula	Not independently re-verified in this pass
Molecular weight	Not independently re-verified in this pass
CAS Registry Number	Not independently re-verified in this pass
PubChem CID	Not independently re-verified in this pass
Peptide class	Growth hormone secretagogue (ghrelin receptor agonist family)
Primary biological target	Ghrelin receptor (GHS-R1a)
Developer or originator	Developed in the 1980s-1990s as a growth-hormone-releasing research tool; marketed in Japan by Kaken Pharmaceutical
Development status	Approved diagnostic agent in Japan only; not developed as a therapeutic elsewhere

What is GHRP-2?

GHRP-2 stands for growth hormone releasing peptide-2. It is a small, lab-made peptide — six amino acids strung together with a couple of unusual, non-standard building blocks — that was designed to make the pituitary gland release more growth hormone. It belongs to a family of compounds called growth hormone secretagogues, which work by mimicking a natural hormone called ghrelin (best known as the “hunger hormone”) rather than by mimicking growth hormone-releasing hormone (GHRH), the body’s main natural signal for growth hormone release.

GHRP-2 was developed out of research into synthetic growth-hormone-releasing peptides that began in the 1980s at Tulane University under Cyril Bowers and colleagues, the same research group credited with much of the early GHRP family (including GHRP-6). GHRP-2 itself is generally credited to later refinement work, including by Kaken Pharmaceutical in Japan, which eventually brought it to market there as a diagnostic agent under the brand name GHRP Kaken 100 (pralmorelin hydrochloride), used to help evaluate growth hormone deficiency by measuring how much GH a patient’s pituitary releases after a single injection.

Outside that one approved Japanese diagnostic use, GHRP-2 has been studied in various clinical and academic settings — mostly small pharmacology studies looking at how much growth hormone it releases, how it compares with other secretagogues, and how it behaves when combined with GHRH-type peptides — but it was never developed into an approved treatment for growth hormone deficiency, muscle wasting, or any other condition in the United States, the EU, or most other countries. Today it is sold widely as an unapproved “research chemical” through peptide vendors, and it has a large presence in bodybuilding and anti-aging communities, where it is used off-label and unsupervised.

How does it work?

Plain-English explanation

GHRP-2 works by plugging into the same receptor that the natural hunger hormone ghrelin uses — called the growth hormone secretagogue receptor, or GHSR. When GHRP-2 activates that receptor in the pituitary gland, the gland responds by releasing a pulse of growth hormone into the bloodstream. Because ghrelin also drives appetite, GHRP-2 and its relatives tend to increase hunger as a side effect of the same mechanism that raises growth hormone.

Technical explanation

GHRP-2 is a GHSR-1a agonist. Binding at the pituitary somatotroph GHSR triggers a signaling cascade (largely through phospholipase C and intracellular calcium) that stimulates pulsatile GH release, largely independent of, but synergistic with, the hypothalamic GHRH pathway. Because it works through a separate receptor than GHRH, combining GHRP-2 with a GHRH analog produces a larger GH pulse than either compound alone — a synergy that has been repeatedly demonstrated in human pharmacodynamic studies and is the basis for most “GHRP + GHRH” stacking discussed in research and community settings. GHRP-2 also has mild, dose-dependent effects on cortisol, prolactin, and ACTH release at higher exposures, which is thought to reflect some degree of non-selective receptor activation in the hypothalamic-pituitary axis.

Potential benefits and research applications

Diagnostic use in growth hormone deficiency testing (human clinical evidence, approved use in Japan only)

What is being investigated: whether a single GHRP-2 injection can reliably provoke a GH response large enough to distinguish a normally functioning pituitary from one that is deficient. How the effect might occur: through direct GHSR agonism at the pituitary, producing a measurable GH spike within roughly an hour of dosing. Evidence: this is the one use of GHRP-2 that has been formally validated and approved, specifically in Japan. Strength: this represents genuine human clinical evidence for a single, narrow, medically supervised diagnostic purpose. Limitation: approval and validated protocols exist in Japan; GHRP-2 is not approved as a diagnostic agent in the United States, the EU, or most other jurisdictions, and this diagnostic-context evidence does not establish that GHRP-2 is safe or effective for repeated self-administration outside a clinical setting.

Increasing growth hormone and IGF-1 levels (human pharmacology evidence)

What is being investigated: whether repeated GHRP-2 dosing meaningfully raises GH and downstream IGF-1 levels over time, similar to how it is used acutely in diagnostic testing. How the effect might occur: repeated GHSR agonism producing repeated GH pulses, which over time can raise circulating IGF-1. Evidence: small pharmacology studies in healthy volunteers and some patient populations have shown that GHRP-2 reliably provokes an acute GH pulse; less is published on sustained, longer-term dosing regimens outside the diagnostic-test context. Strength: acute GH-releasing effect is well documented; sustained-use efficacy and safety data are comparatively thin. Limitation: most published human data reflects single or short-term dosing for research or diagnostic purposes, not the daily, multi-month regimens commonly described online.

Appetite stimulation (human and mechanistic evidence)

What is being investigated: GHRP-2’s orexigenic (appetite-increasing) effect, sometimes explored for wasting or cachexia-type conditions. How the effect might occur: through the same GHSR pathway that mediates ghrelin’s natural hunger signal. Evidence: appetite stimulation is a consistently reported effect in human pharmacology studies of ghrelin-receptor agonists as a class. Strength: this mechanistic link is well established for the receptor family; GHRP-2-specific clinical development for appetite/cachexia indications has not been established. Limitation: no approved cachexia or appetite-disorder indication exists for GHRP-2.

Muscle gain, fat loss, and recovery claims (community-reported, largely unestablished)

What is being investigated: whether elevated GH/IGF-1 from repeated GHRP-2 use meaningfully changes body composition, recovery, or athletic performance in healthy adults. How the effect might occur: theoretically through sustained elevation of GH and IGF-1, both of which have some role in protein synthesis and lipolysis. Evidence: this is almost entirely anecdotal — reported in bodybuilding and peptide-community forums rather than in controlled human trials of GHRP-2 itself. Strength: has not been established in controlled human research. Limitation: no peer-reviewed trial has evaluated GHRP-2 for body-composition or performance outcomes in healthy adults; these claims should be read as community-reported, not clinically demonstrated.

What dosage information circulates?

Figures in this section summarize amounts and schedules reported in published research or circulating online. Their inclusion documents what is reported and does not establish that a regimen is verified, safe, effective, or appropriate.

Amounts studied in human research

GHRP-2 has been used in human pharmacology and diagnostic studies, generally as a single injected dose (commonly by intravenous or subcutaneous route in research settings) used to provoke and measure an acute GH response, and in the approved Japanese diagnostic product as a single injection for GH-deficiency testing. This session could not independently verify the specific milligram/microgram dose used in the approved Japanese diagnostic protocol or in each individual published pharmacology study from primary sources; readers should treat any single specific number attributed to “the clinical dose” of GHRP-2 with caution unless it is traced to the Kaken prescribing information or a named peer-reviewed study.

Amounts studied in animal research

Not consistently reported. GHRP-2 has been used in various animal pharmacology and mechanistic studies of the GHSR pathway, but a consolidated, verifiable set of animal dosing figures specific to GHRP-2 was not identified in this research pass.

Practitioner and community-reported protocols

Peptide vendor sites and bodybuilding/anti-aging forums very widely and consistently describe GHRP-2 doses in the range of roughly 100 to 300 micrograms per injection, given subcutaneously two to three times per day (commonly on waking, pre-workout, and before bed), sometimes combined with a GHRH-type peptide such as CJC-1295 or sermorelin. This 100-300 mcg range is widely repeated online, but its original source could not be verified — it does not appear to trace back to a specific published clinical protocol, and different vendor and forum sources give slightly different sub-ranges without citing a common origin. Community sources describe this as “self-experimentation” dosing, not a validated clinical regimen, and cycle lengths, break periods, and titration patterns vary widely and inconsistently between sources.

Side effects, risks, and limitations

Reported effects associated with GHRP-2 and closely related GHSR agonists in human pharmacology studies include increased appetite/hunger, transient flushing, mild water retention, and dose-dependent increases in cortisol and prolactin at higher exposures. Long-term safety data from repeated, unsupervised self-administration has not been established in controlled human research, because GHRP-2 has not been studied that way in a formal clinical trial setting. Community and practitioner reports mention lethargy, water retention, and increased hunger as recognized nuisance effects; these are anecdotal and not systematically documented. Because GHRP-2 sold outside Japan’s approved pharmaceutical product is an unregulated research chemical, additional risks apply that are unrelated to the molecule’s pharmacology itself: unverified purity, unverified concentration, contamination, and unsterile compounding are recognized risks with any unregulated injectable peptide, and have not been evaluated for any specific vendor supply of GHRP-2.

Regulatory and developmental status

GHRP-2 (pralmorelin) is approved in Japan, marketed by Kaken Pharmaceutical as a diagnostic agent (GHRP Kaken 100) used to help evaluate growth hormone deficiency in a clinical setting. It is not approved by the U.S. Food and Drug Administration or the European Medicines Agency for any human indication, diagnostic or therapeutic, and is not legally marketed in the United States as a drug or dietary supplement; peptides sold as “GHRP-2” in research-chemical channels are unapproved and not FDA-regulated for human use. Development beyond the Japanese diagnostic indication (for example, for growth hormone deficiency treatment or short stature) reached only early-stage clinical investigation and was not carried through to broader approval.

Frequently asked questions

What is GHRP-2?

GHRP-2 is a synthetic six-amino-acid peptide that stimulates the pituitary gland to release growth hormone by activating the ghrelin receptor (GHSR). It is approved in Japan as a diagnostic test for growth hormone deficiency and is otherwise sold as an unapproved research chemical.

How does GHRP-2 work?

It binds the same receptor that the natural hunger hormone ghrelin uses, triggering the pituitary gland to release a pulse of growth hormone. This is a different mechanism than GHRH-type peptides, which is why the two are often studied and used together.

What dosage has been studied in humans?

GHRP-2 has been used as a single dose in pharmacology and diagnostic research to provoke and measure a GH response. This session could not independently verify a specific standardized clinical microgram dose from primary sources.

What dosage commonly circulates online?

Vendor and forum sources widely describe roughly 100 to 300 micrograms per subcutaneous injection, given two to three times daily. This figure is widely repeated but its original source could not be verified.

Has GHRP-2 been studied in humans?

Yes, in small pharmacology and diagnostic studies, and it is an approved diagnostic product in Japan. It has not been studied as an approved treatment peptide for muscle gain, fat loss, or anti-aging use.

What side effects have been reported?

Increased hunger, mild flushing, water retention, and dose-dependent increases in cortisol and prolactin have been reported in pharmacology research and community use. Long-term safety from unsupervised self-administration has not been established.

Is GHRP-2 approved for use?

Only in Japan, and only as a diagnostic agent for growth hormone deficiency testing. It is not approved as a treatment anywhere, and is not an approved drug or supplement in the United States.

How strong is the evidence for GHRP-2’s effects?

The acute GH-releasing effect is well documented in human pharmacology research. Claims about muscle gain, fat loss, or anti-aging benefits from repeated self-administration are not supported by controlled human trials and remain anecdotal.

What remains unknown about GHRP-2?

The safety and effects of repeated, long-term, unsupervised dosing in healthy adults have not been established. The original source of the commonly circulated 100-300 mcg community dosing range could not be traced.

Bottom line

GHRP-2 is a genuine growth-hormone-releasing peptide with real human pharmacology behind its acute GH-stimulating effect, and it holds a narrow, approved diagnostic role in Japan. Beyond that specific and medically supervised use, GHRP-2 has not been established as a safe or effective treatment for muscle gain, fat loss, or anti-aging purposes. The dosing figures that circulate in bodybuilding and peptide communities are widely repeated but not traceable to a validated clinical protocol, and anyone encountering GHRP-2 outside its approved Japanese diagnostic context should understand it as an unapproved, unregulated research chemical with unresolved long-term safety questions.