GHRP-2 (Pralmorelin): A Literature Course in Six Modules

This six-module course summarises what the published literature has reported about GHRP-2, the synthetic peptide also known by the international non-proprietary name pralmorelin. Each module describes what researchers did, what they measured and what they reported, and then closes with the limits of that evidence. This page is for educational purposes only and is not medical advice; consult a licensed physician about any medical question, symptom or treatment decision.

Module 1: What GHRP-2 Is and How It Has Been Studied

GHRP-2 is a small synthetic peptide belonging to the class of compounds described in the literature as growth hormone secretagogues — molecules that provoke growth hormone (GH) release by a route distinct from growth hormone-releasing hormone (GHRH). A drug-development profile catalogued the compound under multiple designations, including pralmorelin, GHRP-2, GPA-748, KP-102, KP-102 D and KP-102 LN, reflecting both injectable and alternative-route development codes (PMID 15230633).

The compound sits historically in the growth hormone-releasing peptide series, synthetic analogues developed before the endogenous ligand ghrelin was identified. Once ghrelin was characterised, later papers grouped GHRP-2 with ghrelin as an agonist at the same receptor, and several studies compared the two side by side; one avian study tested chicken ghrelin and GHRP-2 in parallel in the same model (PMID 12393062).

How the literature has approached it

• Human provocative endocrine testing. The largest body of clinical work used GHRP-2 as a single-administration diagnostic stimulus, including a study of the GHRP-2 test in hypothalamic-pituitary disorder (PMID 35795807) and an evaluation of the test in thyrotropin-producing pituitary adenomas (PMID 29973439).
• Paediatric endocrine testing. Researchers described the GH response to GHRP-2 in children (PMID 20662346).
• Animal models. Work in GH-deficient little mice examined whether the GH response survived a defective GHRH pathway (PMID 22473409), and a general pharmacology study characterised KP-102 across organ systems (PMID 15646371).
• In-vitro and cell work. One study applied GHRP-2 to human ovarian granulosa cells under an inflammatory stimulus (PMID 27548147); another examined mouse pituitary tissue (PMID 19682503).
• Formulation chemistry. Chemists synthesised a mono-PEGylated GHRP-2 conjugate and investigated its biological activity (PMID 25761386).

Limits of the evidence in Module 1

The literature reviewed here is fragmentary rather than cumulative. It contains diagnostic-testing reports, isolated animal and cell experiments and a chemistry paper, but no long-term randomised human trials of repeated administration. Naming conventions also complicate reading: the same molecule appears as pralmorelin, GHRP-2 and KP-102 across papers, so studies that look unrelated may concern one compound.

Module 2: Mechanism as Described in the Literature

The mechanism most consistently described is agonism at the growth hormone secretagogue receptor — the receptor for which ghrelin is the endogenous ligand — with downstream stimulation of somatotroph secretion. The strongest mechanistic separation from GHRH comes from animal genetics: researchers reported a GH response to GHRP-2 in GH-deficient little mice, an animal model carrying a defective GHRH receptor, indicating that the secretagogue pathway does not require intact GHRH receptor signalling (PMID 22473409).

The literature also describes pituitary actions beyond GH. In mouse pituitary tissue, researchers reported that GHRP-2 stimulated both the secretion and the synthesis of adrenocorticotropic hormone (ACTH), placing the corticotroph axis within the compound's described pharmacology (PMID 19682503). This is consistent with the use of GHRP-2 in clinical testing protocols that examined more than one pituitary axis (PMID 35795807).

Not every neuroendocrine axis responded. A study in healthy men reported that GH-releasing peptide-2 did not stimulate arginine vasopressin secretion, a negative mechanistic result that narrows the range of hypothalamic effects attributable to the peptide (PMID 19907099).

A separate line of work described non-pituitary signalling. In human ovarian granulosa cells, the study reported that GHRP-2 attenuated protein kinase C-induced inflammation, which the authors framed as receptor-mediated activity in peripheral reproductive tissue rather than as an endocrine effect of GH (PMID 27548147). Appetite signalling appears in the same mechanistic family: researchers reported that GHRP-2, like ghrelin, increased food intake in healthy men (PMID 15699539).

Limits of the evidence in Module 2

Mechanistic claims rest on single studies in different species and preparations. A cell-culture finding in granulosa cells describes what a receptor system can do in a dish, not what happens in an intact organism. The mouse pituitary ACTH result has not been paired, in this evidence set, with a comparable controlled human synthesis experiment. Receptor-level questions such as biased signalling, desensitisation with repeated exposure and tissue-specific receptor density were not resolved by these papers.

Module 3: Reported Outcomes by Study

The table below groups each cited study by model, endpoint and reported result. No study in this set was designed to demonstrate a therapeutic benefit, and none is presented here as evidence of one.

Two features of this table deserve emphasis. First, the human work is dominated by diagnostic testing: the endpoint was usually whether a provoked hormone value helped classify a pituitary disorder (PMID 35795807, PMID 29973439), not whether a patient improved. Second, appetite findings moved in opposite directions across species — increased intake in healthy men (PMID 15699539) versus inhibited intake in neonatal chicks (PMID 12393062) — which is a caution against reading any single animal result as a human prediction.

Limits of the evidence in Module 3

None of these studies measured body composition, strength, injury recovery, sleep architecture or long-term health outcomes. Endpoints were hormonal, behavioural (food intake), diagnostic or biochemical. Sample sizes in the human work were those typical of endocrine testing studies, and the cited reports describe short observation windows rather than chronic exposure.

Module 4: GHRP-2 Side Effects: What Studies Report

The published adverse-event record for GHRP-2 is thin and largely descriptive, because most human exposure in the literature was a single administration in a monitored testing setting. The drug-development profile of pralmorelin summarised the compound's development programme, including its tolerability assessment across the codes KP-102 and GPA-748 (PMID 15230633), and the preclinical general pharmacology study examined effects of KP-102 across organ systems, which is the standard framework in which off-target signals are first sought (PMID 15646371).

Effects that are on-target but not necessarily wanted

Several reported effects are pharmacological consequences rather than classic adverse events, and the literature presents them as such:

• Corticotroph activation. Researchers reported that GHRP-2 stimulated ACTH secretion and synthesis in mouse pituitary, meaning stimulation was not confined to the GH axis (PMID 19682503).
• Increased food intake. The study in healthy men reported that GHRP-2 increased food intake, an effect shared with ghrelin (PMID 15699539).
• Multi-axis responses in testing. Diagnostic work using the GHRP-2 test in hypothalamic-pituitary disorder was conducted in supervised clinical settings with hormone monitoring (PMID 35795807).

A reported absence of effect

Negative findings also form part of the safety picture. Researchers reported that GH-releasing peptide-2 did not stimulate arginine vasopressin secretion in healthy men, which argues against water-retention effects mediated by that hormone in that setting (PMID 19907099).

Limits of the evidence in Module 4

There is no long-term safety dataset for GHRP-2 in this evidence set. Single-administration diagnostic studies cannot detect effects that would require weeks or months to appear, such as changes in glucose handling, sustained cortisol elevation, or consequences of chronic GH-axis stimulation. Studies also did not evaluate unregulated products of unverified content, which introduce impurity and mislabelling risks entirely outside the published record. Absence of a reported adverse event in a small short study is not evidence that the event does not occur.

Module 5: Pharmacokinetics Where Data Exist

Dedicated human absorption, distribution, metabolism and excretion studies of GHRP-2 are not represented in this evidence set. What the literature does contain is indirect and formulation-oriented. The development profile listed distinct codes for different presentations of pralmorelin, including KP-102 D and KP-102 LN, indicating that more than one route of administration was pursued during development (PMID 15230633).

The most explicit pharmacokinetic reasoning appears in chemistry work: researchers synthesised a mono-PEGylated GHRP-2 conjugate and investigated whether biological activity was retained, an approach conventionally used to modify the disposition of small peptides (PMID 25761386). The preclinical general pharmacology of KP-102 also characterised the compound as a potent growth hormone-releasing peptide across animal systems, which is a pharmacodynamic rather than pharmacokinetic characterisation (PMID 15646371).

Clinically, the use of GHRP-2 as a provocative test agent implies a rapid onset of measurable hormone response within a testing window, since diagnostic protocols depend on timed sampling after administration (PMID 35795807, PMID 29973439).

Limits of the evidence in Module 5

No half-life, clearance, bioavailability or metabolite profile is stated on this page because the verified literature reviewed here does not supply those figures. Readers should treat any specific pharmacokinetic number circulating without a citation as unverified. The PEGylation paper describes a modified molecule, not the parent peptide, and its findings do not transfer to unmodified GHRP-2.

Module 6: Regulatory Status, Stated Factually

Regulatory status differs sharply by jurisdiction and by intended use.

• Diagnostic use. Pralmorelin has been used as an approved diagnostic agent in Japan, which is why the clinical literature on the "GHRP-2 test" is concentrated in Japanese endocrinology journals, including the 2022 report on hypothalamic-pituitary disorder (PMID 35795807) and the 2018 evaluation in thyrotropin-producing adenomas (PMID 29973439).
• United States. GHRP-2/pralmorelin is not an approved drug product in the United States; the development profile documents it as an investigational compound under several sponsor codes (PMID 15230633). Material offered in the US for laboratory work is typically labelled "research use only" and is not intended for human administration.
• Compounding. US pharmacy compounding of a bulk drug substance requires that the substance meet defined statutory criteria — for example, being a component of an FDA-approved drug, appearing in an applicable monograph, or being listed by FDA as eligible. Substances that do not meet those criteria are not lawfully compounded, and many growth hormone secretagogue peptides have been treated by FDA as raising safety or characterisation concerns.
• Sport. Growth hormone secretagogues, as a class, are prohibited substances under anti-doping rules at all times, in and out of competition.

This section describes regulatory facts for educational context and is not legal advice; rules change and vary by country and state, so verify current status with the relevant authority or a qualified professional.

Limits of the evidence in Module 6

Regulatory approval in one country for a single diagnostic indication says nothing about safety or efficacy for any other use, duration or population. The absence of approval elsewhere reflects regulatory decisions and the state of submitted evidence, not a judgement that can be inferred from the studies summarised above.

Closing: What the Studies Did Not Test

Reading this literature as a whole, the gaps are as informative as the findings:

1. Repeated or long-term administration in healthy adults. The human studies cited were short and diagnostic or single-session in design (PMID 35795807, PMID 15699539).
2. Performance, physique or recovery endpoints. No cited study measured lean mass, strength, fat loss, wound healing or athletic performance.
3. Metabolic safety over time. Glucose tolerance, insulin sensitivity and sustained cortisol exposure were not the endpoints of the studies summarised here, even though ACTH stimulation was reported in mouse pituitary tissue (PMID 19682503).
4. Reproductive and inflammatory outcomes in vivo. The granulosa cell findings were in vitro and were not extended to clinical outcomes (PMID 27548147).
5. Cross-species generalisation. Opposite appetite results in men and in chicks show that the peptide's effects are context-dependent (PMID 15699539, PMID 12393062).
6. Product quality outside regulated supply. Purity, sterility and identity of non-pharmaceutical material were never a subject of these papers.

The accurate one-line summary of the evidence is that GHRP-2 is a well-characterised endocrine probe with a small, mostly short-term literature — and that anything beyond hormone stimulation, diagnostic classification and the specific cell and animal findings described above remains untested in the papers reviewed here.

References

• Clinical Usefulness of the Growth Hormone-Releasing Peptide-2 Test for Hypothalamic-Pituitary Disorder (Journal of the Endocrine Society, 2022)
• Evaluation of growth hormone-releasing peptide-2 for diagnosis of thyrotropin-producing pituitary adenomas (Endocrine Journal, 2018)
• Pralmorelin: GHRP 2, GPA 748, growth hormone-releasing peptide 2, KP-102 D, KP-102 LN, KP-102D, KP-102LN (Drugs in R&D, 2004)
• Growth Hormone Releasing Peptide-2 Attenuation of Protein Kinase C-Induced Inflammation in Human Ovarian Granulosa Cells (International Journal of Molecular Sciences, 2016)
• GH-releasing peptide-2 does not stimulate arginine vasopressin secretion in healthy men (Endocrine Journal, 2010)
• Synthesis of Mono-PEGylated Growth Hormone Releasing Peptide-2 and Investigation of its Biological Activity (AAPS PharmSciTech, 2015)
• Growth hormone response to GH-releasing peptide-2 in children (Journal of Pediatric Endocrinology & Metabolism, 2010)
• Growth hormone-releasing peptide-2 stimulates secretion and synthesis of adrenocorticotropic hormone in mouse pituitary (Regulatory Peptides, 2009)
• Growth hormone releasing peptide-2 (GHRP-2), like ghrelin, increases food intake in healthy men (Journal of Clinical Endocrinology and Metabolism, 2005)
• Growth hormone response to growth hormone-releasing peptide-2 in growth hormone-deficient little mice (Clinics, 2012)
• Chicken ghrelin and growth hormone-releasing peptide-2 inhibit food intake of neonatal chicks (European Journal of Pharmacology, 2002)
• General pharmacology of KP-102 (GHRP-2), a potent growth hormone-releasing peptide (Arzneimittel-Forschung, 2004)