# GHRP-2 — Research Peptide Profile

> Among the most potent GHRPs per microgram, with less hunger than GHRP-6. Human study data, half-life, GH pulse effects & GHRP-2 vs GHRP-6.

Source: https://peptpedia.org/peptide/ghrp-2 | Published: 2025-12-02 | Last updated: 2026-08-04

GHRP-2 (pralmorelin) is among the most potent GHRPs per microgram, with less appetite stimulation than GHRP-6. It has been studied in humans as a diagnostic probe of pituitary GH reserve. It remains an unapproved research compound.

## Overview

GHRP-2 is a synthetic hexapeptide GH secretagogue and potent GHSR-1a agonist, also known as Pralmorelin. Among the major GHRPs, GHRP-2 achieves [the highest GH release per microgram](/compare/ghrp-6-vs-ghrp-2) in most studies while producing less appetite stimulation than [GHRP-6](/peptide/ghrp-6) and less cortisol elevation than [Hexarelin](/peptide/hexarelin). Human clinical studies document 10–15× GH baseline elevations within 30 minutes. Japan approved Pralmorelin for GH deficiency diagnosis, giving it one of the strongest clinical validation profiles among GHRPs.

## Molecular Profile

- **Category:** growth-factors
- **Molecular formula:** C45H55N9O6
- **Molecular weight:** 817.97 g/mol
- **CAS number:** 158861-67-7
- **Amino acid sequence:** D-Ala-D-βNal-Ala-Trp-D-Phe-Lys-NH2
- **Also known as:** Growth Hormone Releasing Peptide 2, Pralmorelin, KP-102
- **Half-life:** 15-60 minutes
- **Solubility:** Soluble in water
- **Storage:** Store lyophilized at -20°C.

## Mechanism of Action

GHRP-2 acts as a potent agonist at the [ghrelin receptor (GHSR-1a)](/research/ipamorelin-ghs-pathway), stimulating growth hormone release from the pituitary. It works synergistically with GHRH analogs through activation of different signaling pathways. GHRP-2 may also have some effects on cortisol and prolactin, though less pronounced than GHRP-6. Its appetite-stimulating effects are moderate compared to GHRP-6.

## Key Research Findings

- GHRP-2 is among the most potent GHRPs for growth hormone stimulation on a per-microgram basis while producing substantially less appetite stimulation than GHRP-6.
- Despite frequent claims that GHRP-2 deepens sleep, a placebo-controlled study found evidence against a role for the GHRP axis in human slow-wave sleep, even though deep sleep and the nocturnal GH pulse naturally coincide.
- GHRP-2 maintains its GH-releasing effectiveness in elderly subjects, with only modest age-related decline compared to the dramatic reduction in natural GH secretion seen with aging.
- GHRP-2 has been formally studied as a diagnostic tool for assessing pituitary GH reserve, giving it a clinical validation path distinct from most research peptides.

## Dosing Information (Research Context)

Research protocols typically use 100-300 mcg administered 2-3 times daily. The peptide is often studied in combination with GHRH analogs.

| Route | Dose | Frequency | Notes |
| --- | --- | --- | --- |
| Subcutaneous | 1–3 mcg/kg (or 100–300 mcg) | 1–3× daily | Peak GH at 15–30 min; standard research dosing |
| Intravenous | 1 mcg/kg | Single dose | Used in GH pituitary reserve diagnostic protocols in Japan |

## Researched Effects

- **Potent GH Release** (evidence: extensive): Research consistently demonstrates GHRP-2 (Pralmorelin) as one of the most potent growth hormone secretagogues available for research, producing robust GH elevations through high-affinity binding to the growth hormone secretagogue receptor (GHSR-1a) on pituitary somatotroph cells. Clinical studies document peak plasma GH concentrations of 30-100 ng/mL occurring approximately 15-30 minutes after subcutaneous administration, representing 8-20 fold increases above baseline levels depending on dosage and individual response characteristics. GHRP-2's potency for GH stimulation exceeds that of GHRP-6 on a microgram-per-microgram basis while producing less pronounced side effects on appetite and cortisol, making it particularly valuable for growth hormone deficiency treatment studies. The peptide maintains effectiveness in elderly subjects with diminished natural GH production, demonstrating consistent GH responses that decline only modestly with age compared to younger populations. Research protocols frequently combine GHRP-2 with GHRH analogs such as CJC-1295 or Sermorelin for synergistic growth hormone amplification, with studies showing 2-3 fold greater GH release compared to either compound alone.
- **IGF-1 Elevation** (evidence: extensive): Studies demonstrate significant and sustained elevation of insulin-like growth factor 1 (IGF-1) following GHRP-2-induced growth hormone release, with effects persisting beyond the acute GH peak due to the downstream nature of IGF-1 production in the liver. Research shows IGF-1 increases of 25-75% above baseline within 7-14 days of consistent GHRP-2 administration, with levels stabilizing at elevated plateaus during continued treatment protocols. The IGF-1 elevation mediates many of GHRP-2's anabolic effects including enhanced protein synthesis, improved nitrogen retention, and accelerated muscle recovery optimization following resistance exercise in research models. Studies in growth hormone deficiency models demonstrate normalization of IGF-1 levels with appropriate GHRP-2 dosing, suggesting potential applications in growth hormone replacement therapy research. The relationship between GHRP-2 dosing and IGF-1 response provides researchers with a predictable biomarker for assessing treatment efficacy in various endocrine research applications including age-related hormone decline studies.
- **Moderate Appetite Effects** (evidence: moderate): GHRP-2 produces significantly less appetite stimulation compared to GHRP-6, typically causing mild hunger increases in approximately 30-40% of research subjects compared to the near-universal appetite effects observed with GHRP-6. This reduced ghrelin-mimetic activity at hypothalamic appetite centers makes GHRP-2 particularly suitable for metabolic research studies where hunger confounds would complicate data interpretation. Research indicates GHRP-2's modest appetite effects result from lower intrinsic activity at the orexigenic signaling pathways downstream of GHSR-1a activation compared to its robust GH-releasing potency. The balanced profile between GH stimulation and appetite modulation positions GHRP-2 as an ideal research tool for body composition studies, muscle protein synthesis research, and investigations where maintaining controlled feeding conditions is essential. Studies comparing GHRP family members consistently rank GHRP-2 between Ipamorelin (minimal appetite effects) and GHRP-6 (strong appetite effects) on the spectrum of hunger induction.
- **Sleep Research** (evidence: preliminary): The relationship between GHRP-2 and sleep is frequently discussed because slow-wave (deep) sleep naturally coincides with the largest nocturnal growth hormone pulse. However, controlled human data do not support the idea that GHRP-2 enhances slow-wave sleep: a placebo-controlled polysomnography study found evidence against a role for the GHRP axis in human slow-wave sleep, despite the temporal correlation between deep sleep and nocturnal GH secretion. Interest remains in clarifying how growth hormone secretagogues interact with sleep architecture—particularly in aging, where both GH secretion and slow-wave sleep decline—but current evidence does not establish GHRP-2 as a sleep-enhancing agent.

## Research Applications

- Endocrinology
- GH Research
- Metabolism Studies
- Sleep Research

## Key Studies

### Growth hormone-releasing peptide-2 infusion synchronizes growth hormone, thyrotrophin and prolactin release in prolonged critical illness

Van den Berghe G, et al. — *European Journal of Endocrinology* (1999) — [PMID 10037246](https://pubmed.ncbi.nlm.nih.gov/10037246/) | [doi:10.1530/eje.0.1400017](https://doi.org/10.1530/eje.0.1400017)

This clinical study investigated whether continuous GHRP-2 infusion synchronizes the release of multiple anterior pituitary hormones including growth hormone (GH), thyrotrophin (TSH), and prolactin (PRL) in patients with prolonged critical illness. Researchers sampled blood every 20 minutes over 9 hours during 21-hour infusions of placebo, GHRH, GHRP-2, TRH, or their combinations, then quantified temporal coupling among the hormones using cross-correlation analysis of 86 serum concentration time series. The normal synchrony among GH, TSH, and PRL was absent during placebo delivery, and infusion of GHRP-2 — but not GHRH or TRH — markedly synchronized the serum profiles of all three hormones (all P<=0.007). Adding GHRH and TRH to GHRP-2 maintained and further enhanced the GH-PRL synchrony. The authors concluded that this synchronizing effect, unique to GHRP-2, suggests that a presumed endogenous GHRP-like ligand may participate in orchestrating coordinated anterior pituitary hormone release.

### Pharmacokinetics and pharmacodynamics of growth hormone-releasing peptide-2: a phase I study in children

Pihoker C, Bowers CY, et al. — *Journal of Clinical Endocrinology and Metabolism* (1998) — [PMID 9543135](https://pubmed.ncbi.nlm.nih.gov/9543135/) | [doi:10.1210/jcem.83.4.4744](https://doi.org/10.1210/jcem.83.4.4744)

This Phase I clinical study characterized the pharmacokinetics and pharmacodynamics of GHRP-2 in children, providing early human data on the peptide's absorption, clearance, and growth-hormone-releasing activity. Administration produced dose-dependent increases in growth hormone secretion, and the study defined plasma pharmacokinetic parameters supporting practical dosing. Co-authored by GHRP co-discoverer Cyril Bowers, the work helped establish GHRP-2 as a potent and well-tolerated growth hormone secretagogue in humans and informed its later use as a diagnostic agent for assessing pituitary GH reserve.

### Evidence against a role for the growth hormone-releasing peptide axis in human slow-wave sleep

Moreno-Reyes R, Kerkhofs M, et al. — *American Journal of Physiology* (1998) — [PMID 9612233](https://pubmed.ncbi.nlm.nih.gov/9612233/) | [doi:10.1152/ajpendo.1998.274.5.E779](https://doi.org/10.1152/ajpendo.1998.274.5.E779)

This placebo-controlled study tested whether the growth-hormone-releasing peptide (GHRP) axis contributes to the regulation of slow-wave (deep) sleep in healthy adults, using polysomnography with concurrent hormone sampling. Contrary to the hypothesis that GHRPs promote deep sleep, the investigators found that GHRP administration did not produce a meaningful enhancement of slow-wave sleep, providing evidence against a causal role for the GHRP axis in human slow-wave sleep. Although nocturnal growth hormone secretion and slow-wave sleep are temporally correlated, the results indicate this association does not reflect a direct GHRP-driven promotion of deep sleep—an important caution against assuming GHRP-2 improves sleep quality.

## Frequently Asked Questions

### Is GHRP-2 more potent than GHRP-6?

Yes, GHRP-2 produces greater GH release per microgram compared to GHRP-6 in most published studies—clinical data show 10–15× baseline GH elevations. Additionally, GHRP-2 produces less appetite stimulation than GHRP-6 (a moderate vs. near-universal hunger response) and has less cortisol and prolactin elevation at standard doses. This combination of high GH potency with fewer off-target effects makes GHRP-2 preferred for research focused on GH/IGF-1 effects without appetite or cortisol confounders.

### Has GHRP-2 been approved for any medical use?

Yes. GHRP-2 (under the pharmaceutical name Pralmorelin) is approved in Japan as a diagnostic agent for assessing pituitary GH reserve in adults suspected of GH deficiency. This makes GHRP-2 one of the few GHRPs with actual regulatory approval in any country. It is not approved for therapeutic GH replacement use anywhere. This diagnostic approval provides a higher level of clinical validation than most research peptides.

### How does GHRP-2 affect sleep quality?

Despite popular claims that GHRP-2 deepens sleep, the controlled evidence does not support this. A placebo-controlled polysomnography study (PMID: 9612233) found evidence against a role for the growth-hormone-releasing peptide axis in human slow-wave sleep—GHRP administration did not meaningfully increase deep sleep. Slow-wave sleep and the nocturnal GH pulse are temporally correlated because both are driven by overlapping hypothalamic circuits, but that correlation does not mean GHRP-2 itself enhances sleep. GHRP-2 should not be assumed to improve sleep quality based on current human data.

### How does GHRP-2 compare to Hexarelin?

Both are highly potent GHRPs, but Hexarelin tends to produce more cortisol and prolactin elevation, and more receptor desensitization (tachyphylaxis) with repeated dosing. GHRP-2 maintains more consistent GH response across repeated administrations and has less pronounced cortisol effects, making it better for ongoing research protocols. Hexarelin has stronger documented cardioprotective effects through direct CD36 receptor activation that is independent of GH release—an effect not well-characterized for GHRP-2.

### Can GHRP-2 be used to test pituitary function?

Yes. In Japan, Pralmorelin (GHRP-2) is used as a pituitary function test—intravenous administration allows clinicians to measure peak GH response and assess the pituitary's GH reserve capacity. A robust GH response (typically > 9 ng/mL) suggests an intact somatotroph population, while a blunted response indicates potential GH deficiency. This diagnostic application is more specific to pituitary function than conventional insulin tolerance tests and avoids the hypoglycemia risks of older testing methods.

### Does GHRP-2 cause desensitization with repeated use?

Research suggests GHRP-2 causes less receptor desensitization (tachyphylaxis) than Hexarelin with repeated dosing protocols. However, some reduction in GH response can occur with very frequent administration (multiple times daily for extended periods). The mechanism involves downregulation of GHSR-1a at the pituitary and potential increases in somatostatin tone. Spacing doses to allow full receptor recovery (typically 2+ hours between injections) helps maintain response consistency.

### What research has studied GHRP-2's effects on body composition?

GHRP-2 studies in GH-deficient adults document improvements in lean body mass (1.5–3 kg over 3–6 months), reductions in visceral adiposity, and improved IGF-1 levels. A 3-month double-blind study in elderly subjects showed increased nitrogen retention and reduced fat mass with 100 mcg three times daily. Effects are GH-dependent and mediated through hepatic IGF-1 production. Body composition changes are generally comparable to exogenous GH administration at equivalent GH elevations—supporting GHRP-2's use in GH-deficiency body composition research.

### What is GHRP-2's standard research dosing protocol?

In published human studies, GHRP-2 is typically administered subcutaneously at 100–300 mcg per dose, 1–3 times daily. The most common research protocol is 100 mcg three times daily (morning, midday, evening) with the evening dose timed 30–60 minutes before sleep to amplify nocturnal GH pulsatility. For diagnostic pituitary function testing (Pralmorelin test in Japan), 2 mcg/kg IV is the standardized dose. GHRP-2 is frequently combined with GHRH/CJC-1295 to achieve synergistic GH release.

## Related Peptides

- [Ipamorelin](https://peptpedia.org/peptide/ipamorelin)
- [GHRP-6](https://peptpedia.org/peptide/ghrp-6)
- [Hexarelin](https://peptpedia.org/peptide/hexarelin)
- [CJC-1295](https://peptpedia.org/peptide/cjc-1295)

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This content is for educational and research purposes only. It is not medical advice, and the compounds covered are research chemicals not approved for human use unless explicitly stated otherwise.

Cite this page: Peptpedia — Research Peptide Encyclopedia, https://peptpedia.org