GHRP-2

GHRP-2: D-Ala-D-2Nal-Ala-Trp-D-Phe-Lys-NH2. Hexapeptide (6 amino acids). MW 817.97 Da. The sequence contains three D-amino acids (D-Ala at position 1, D-2Nal at position 2, D-Phe at position 5) — standard GHRP structural feature that confers metabolic stability and GHS-R1a binding geometry. The D-2Nal (D-beta-naphthylalanine) residue at position 2 is unique to GHRP-2 within the GHRP family and is the primary structural difference from GHRP-6 (which has His-D-Trp at positions 1-2). The D-2Nal modification increases GHS-R1a affinity and alters the receptor interaction geometry in ways that marginally differentiate GHRP-2's pharmacological profile from GHRP-6 — higher GH potency, less appetite stimulation, essentially similar cortisol elevation.

Plasma half-life: approximately 15-30 minutes following subcutaneous injection. Time to peak GH response: approximately 15-30 minutes post-injection. Duration of GH pulse: approximately 60-90 minutes total from injection. Metabolism: peptidase-mediated cleavage in plasma and tissues. The GHRP-2 stimulation test uses IV administration (1-2 mcg/kg IV, peak GH at 30-45 minutes); community SubQ use follows the same basic kinetics with somewhat delayed onset. The short half-life means each injection produces a discrete GH pulse — the compound does not produce sustained GH elevation. This is the fundamental pharmacodynamic argument for multiple daily injections and for co-administration with GHRH analogs (which have longer action and provide the hormonal substrate for the pulse that GHRP-2 triggers).

Compound

GH Potency

Cortisol/ACTH

Prolactin

Appetite

Selectivity

Regulatory Status

Hexarelin

Highest (acute)

Highest

High

Moderate

Lowest

Research chemical only; Category 2

GHRP-2 (pralmorelin)

Very high

Moderate-high (= hCRH)

Moderate

Moderate (+35.9% in human)

Low

Japan approved (diagnostic); US Category 2; WADA banned

GHRP-6

High

Moderate-high (≈GHRP-2)

Moderate

High (most of class)

Low

Research chemical only; Category 2

Ipamorelin

Moderate-high

Minimal — does not elevate

Minimal

Minimal

Very high (GH-selective)

Research chemical; regulatory status in flux 2026; WADA banned

MK-677 (oral)

High (24hr IGF-1 elevation)

Low

Low

Significant (orexigenic)

Moderate

Research chemical; oral; non-peptide

GHS-R1a on anterior pituitary somatotrophs: GHRP-2 binding → Gq/11 coupling → phospholipase C (PLC) activation → IP3 generation → intracellular calcium release from ER → DAG generation → PKC activation → calcium influx through voltage-gated channels → GH secretory granule exocytosis. This calcium-mediated release cascade is the primary GH pulse mechanism. Simultaneously, GHRP-2 inhibits somatostatin release from hypothalamic neurons — somatostatin is the main inhibitory brake on GH pulsatility. By both stimulating the accelerator and releasing the brake, GHRP-2 produces GH pulses substantially larger than either GHRH activation or somatostatin suppression alone would achieve.

GHRH (growth hormone releasing hormone) activates GHRH receptors on somatotrophs via cAMP/PKA — a completely different second messenger cascade from GHRP-2's PLC/calcium pathway. When both pathways are active simultaneously — GHRH loading the secretory machinery via cAMP while GHRP-2 triggers release via calcium — the result is additive to synergistic. Bowers 1990 documented this in humans; Veldhuis documented ~3-5x GH output with the combination vs either alone. This synergy is the mechanistic basis for the community's standard GHRP-2 + CJC-1295 stack. CJC-1295 (the GHRH analog) activates GHRH receptors; GHRP-2 activates GHS-R1a. Each pathway amplifies the other's GH output.

THE CORTISOL CO-RESPONSE IS NOT A MINOR SIDE EFFECT

When GHRP-2 binds GHS-R1a in the hypothalamus, it triggers corticotropin-releasing hormone (CRH) release. CRH → pituitary corticotrophs → ACTH → adrenal cortex → cortisol. Arvat et al. (1997), the pivotal human pharmacology study, measured ACTH and cortisol responses to GHRP-2 at multiple dose levels and found: all doses of GHRP-2 stimulated ACTH and cortisol to a degree comparable to hCRH (human corticotropin-releasing hormone) itself. This is not a trivial co-secretion. hCRH-equivalent cortisol activation with every GH-releasing injection means: (1) catabolic hormonal signal alongside the anabolic one; (2) visceral fat accumulation potential; (3) HPA axis strain with multiple daily doses; (4) potential interference with sleep architecture from cortisol elevation. Users taking GHRP-2 3x daily are administering something approaching hCRH-equivalent cortisol signals 3x daily alongside each GH pulse. The net anabolic/catabolic balance is less favorable than the GH pulse alone would suggest.

Ghrelin — the endogenous ligand for GHS-R1a — is the primary orexigenic (appetite-stimulating) hormone in the body, produced by the stomach before meals to signal hunger to the hypothalamus. GHRP-2, as a GHS-R1a agonist, partially mimics this appetite effect. Laferrere et al. (JCEM, 2005): 7 healthy lean males, subcutaneous GHRP-2 infusion (1 mcg/kg/h) vs saline for 270 minutes, then ad libitum buffet meal. GHRP-2 subjects ate 35.9% more food than saline controls. This is the only controlled human measurement of GHRP-2's food intake effect — it is real, clinically meaningful in magnitude, and directly relevant to any body composition application. For cachexia or wasting conditions: this appetite effect is therapeutically valuable. For fat-loss phases: 35.9% increased ad libitum intake fighting against a caloric deficit is a significant practical problem that community users regularly underestimate.

GHRP-2 and other members of the GHRP family bind not only to GHS-R1a but also to the scavenger receptor CD36, which is expressed on cardiomyocytes, hepatic cells, neurons, and immune cells. CD36-mediated signaling activates PI3K/Akt1 prosurvival pathways, reduces ROS production, and reduces apoptosis. In animal models, GHRP-2 and GHRP-6 show cytoprotective effects in cardiac ischemia, hepatic injury, and gastrointestinal mucosal damage — partially or fully independent of GH release. The GH-independent cytoprotection is an underappreciated aspect of the GHRP class. Grade C-D: consistent preclinical evidence; not the basis for community use but relevant to understanding why GHRPs are being studied for organ protection in critical illness.

Bowers CY, Reynolds GA, Durham D et al. (1990, JCEM): the original human confirmation that GHRP-2 stimulates GH in normal volunteers and acts synergistically with GHRH. This established the basic pharmacodynamic profile of GHRP-2 in humans and demonstrated the GHRH synergy that underlies the combination stack. Standard reference for community understanding of why GHRP-2 + GHRH analog produces dramatically larger GH responses than either alone.

The dose-saturation curve: GH response to GHRP-2 increases with dose up to approximately 1-2 mcg/kg (roughly 70-140 mcg for a 70 kg adult), after which the response plateaus. Community convention for the saturation dose: 100 mcg. Above 100 mcg, additional GHRP-2 does not meaningfully increase GH output — it only increases cortisol and prolactin co-secretion. This saturation ceiling is one of the most practically important pharmacodynamic facts for dosing protocols.

Arvat E, Maccagno B, Broglio F et al. (1997, JCEM): the definitive human characterization of GHRP-2's hormonal co-effects. Multiple doses (0.1, 0.5, 1.0 mcg/kg IV) were administered and GH, cortisol, ACTH, and prolactin were measured alongside responses to GHRH, TRH, and hCRH. Findings: all doses of GHRP-2 produced ACTH and cortisol elevation comparable in magnitude to hCRH; all doses produced prolactin elevation (below TRH-induced prolactin, but measurable and dose-dependent). GH response was dose-dependent and large. This study is the definitive human evidence that GHRP-2's cortisol co-secretion is not trivial — it is a real, dose-dependent, hCRH-magnitude hormonal activation with every injection.

Laferrere B, Abraham C, Russell CD, Bowers CY. (2005, JCEM): 7 healthy lean males; GHRP-2 infusion (1 mcg/kg/h) for 270 minutes; ad libitum buffet meal immediately after. GHRP-2 subjects ate 35.9% ± 10.9% more than during saline infusion (p<0.05). GH levels were significantly elevated (confirming the compound was working). This is the only controlled human food intake study for GHRP-2; small n (7), but the direction and mechanism (GHS-R1a orexigenic effect consistent with ghrelin's known biology) are well-supported. The practical implication: GHRP-2 produces meaningful, appetite-stimulating effects in humans comparable to ghrelin.

The GHRP-2 stimulation test: standard dose of 1-2 mcg/kg IV; GH peak measured at 15, 30, 45, 60, 90, and 120 minutes post-injection; GH deficiency diagnosed if peak GH <3-5 ng/mL depending on clinical context and assay. Multiple Japanese and European validation studies confirm its diagnostic accuracy. Comparison to the ITT: the GHRP-2 test produces comparable sensitivity and specificity to the insulin tolerance test for GH deficiency diagnosis, without the hypoglycemia and cardiovascular risks of the ITT. This is the most rigorous clinical validation of GHRP-2's GH-releasing pharmacology — the Japanese regulatory agency was sufficiently confident in the compound's reproducibility and safety profile to approve it as a diagnostic agent.

Mericq V, Bowers CY, Mejia G, Patiño L, Avila A (1998): 8-month study of GHRP-2 in prepubertal GH-deficient children with stepwise increasing doses. GHRP-2 significantly increased GH secretion and IGF-1 levels without significant adverse effects at doses studied. This early study demonstrated that GHRP-2 could produce clinically meaningful IGF-1 elevation in a GH-deficient population. The target application for GHRP-2 in endocrinology was always clinical GH deficiency, not performance enhancement.

Growth hormone is not secreted continuously — it is released in discrete pulses, with the largest occurring during the first deep sleep cycle. Daytime pulses are smaller and more frequent. Somatostatin, the inhibitory hormone, suppresses GH release between pulses. The goal of GHRP-2 protocol design is to amplify existing natural GH pulses by timing doses to coincide with periods of low somatostatin tone and high natural GHRH activity — not to add random GH stimulation at arbitrary times. The three periods of lowest somatostatin and highest responsiveness to GH secretagogues: shortly before sleep (most important), first thing in the morning fasted state, and post-workout fasted state.

100 MCG IS THE CEILING — NOT A STARTING POINT FOR ESCALATION

The GH response to GHRP-2 follows a saturable dose-response: it increases from low doses up to approximately 100 mcg per injection, then plateaus. Above 100 mcg, additional GHRP-2 does not meaningfully increase GH output. What increases above 100 mcg: cortisol co-secretion and prolactin elevation. This is the most important practical fact in GHRP-2 dosing. Users taking 200, 300, or 500 mcg injections are not getting more GH — they are getting more cortisol and more prolactin. The standard community dose (100 mcg) is both the efficacy maximum and the dose at which the cortisol/prolactin co-effects are already near their clinically meaningful peak. There is no upside to exceeding 100 mcg.

Protocol

Dose

Frequency

Timing

Context

Standard GH optimization

100 mcg GHRP-2 + 100 mcg CJC-1295 (no DAC)

2-3x daily

Pre-sleep (most critical); morning fasted; post-workout fasted

Body composition; GH axis support; anti-aging

Conservative

50-100 mcg GHRP-2

Once daily

Pre-sleep only

First-time users; cortisol-sensitive individuals

Appetite/recovery (cachexia context)

100-200 mcg GHRP-2

2-3x daily

Before meals or clinical schedule

Wasting, post-surgery, recovery from illness — appetite stimulation is desired

Diagnostic reference (Japan)

1-2 mcg/kg IV

Single dose

Fasted morning

GH deficiency diagnostic; physician-administered; not community use

Reconstitution: standard peptide preparation with bacteriostatic water. Typical concentration: 2 mg per 2 mL = 1 mg/mL = 1,000 mcg/mL. A 100 mcg dose = 0.1 mL = 10 units on a U-100 insulin syringe. Subcutaneous injection: abdomen, upper thigh, or deltoid area. Rotate sites to prevent lipohypertrophy. Pre-sleep injection: 30-60 minutes before sleep, in a fasted state (no food for 2-3 hours; no carbohydrates or fat in particular, as insulin elevation suppresses GH release). Post-workout: 30-60 minutes after training, fasted if possible. Morning: upon waking before any food.

Insulin and GH are physiologically antagonistic: insulin elevation suppresses GH secretion through hypothalamic somatostatin activation. This is not a minor interaction — eating a carbohydrate-heavy meal before GHRP-2 injection can substantially blunt the GH response. The practical rule: inject in a fasted state (2-3 hours minimum post-meal, no carbohydrates within 1 hour). The pre-sleep injection is most naturally aligned with fasting because the gap between the last meal and bedtime typically provides the required fasted window. Post-workout is the most challenging context for fasting because protein intake for recovery also contains amino acids that can mildly stimulate insulin — though post-workout insulin spikes are more acute and brief than carbohydrate-driven elevations.

Partial tachyphylaxis (receptor desensitization) occurs with chronic daily GHRP-2 use, particularly at high doses and high frequency. GHS-R1a undergoes GRK-mediated phosphorylation and beta-arrestin recruitment following repeated agonist exposure, leading to receptor internalization and reduced responsiveness. The receptor recycling half-life is approximately 60-90 minutes — meaning that the minimum interval between injections for maintained responsiveness is approximately this window, and that more frequent dosing can lead to progressive attenuation. Community cycling practice: 3 months on, 1 month off; or 4 weeks on, 2 weeks off. Pulse-then-rest protocols outperform continuous daily-forever use for sustained GH output over time.

GHRP-2's side effect profile derives directly from its pharmacological mechanisms. Water retention/bloating: GH-mediated increase in renal water reabsorption; common, dose-dependent; reduces with dose reduction. Tingling/numbness in extremities (carpal tunnel-like): GH-mediated fluid retention compresses the carpal tunnel; can progress to true carpal tunnel syndrome with extended high-dose use. Cortisol elevation: the most pharmacologically significant side effect — hCRH-comparable ACTH/cortisol response with each injection; catabolic; disrupts sleep quality if injected close to bedtime; cumulative with multiple daily doses. Prolactin elevation: moderate but measurable; some community users monitor prolactin and use dopamine agonists (cabergoline) if prolactin becomes elevated; less concern than with hexarelin. Appetite stimulation: ~35.9% food intake increase documented in humans; counterproductive for fat-loss phases; beneficial in recovery/cachexia contexts. Injection site reactions: mild; typical for subcutaneous peptide injections.

For the community user taking GHRP-2 specifically for body composition — muscle building, fat loss, body recomposition — the cortisol co-response creates a pharmacological tension worth quantifying. GH elevation: promotes protein synthesis, IGF-1 elevation, fat mobilization — anabolic/lipolytic. Cortisol co-elevation (hCRH magnitude): promotes muscle protein catabolism, visceral fat deposition, impairs insulin sensitivity over time, disrupts deep sleep architecture. Twice-daily GHRP-2 at 100 mcg means two hCRH-comparable cortisol signals per day, in addition to baseline cortisol. Whether the net GH anabolic effect exceeds the cortisol catabolic effect depends on individual cortisol sensitivity, training status, diet, and sleep quality. This trade-off is not present with ipamorelin, which produces GH pulses without meaningful cortisol activation — a major reason the community has largely migrated away from GHRP-2.

The appetite stimulation from GHRP-2 constitutes a behavioral effect requiring the C4 audit. GHS-R1a's role in appetite regulation is not incidental — it is a core function of the ghrelin system. The 35.9% food intake increase documented by Laferrere is acute (hours post-injection) but real. Users in caloric restriction phases report fighting cravings triggered by GHRP-2 injections, particularly in the 1-2 hour post-injection window when hunger is most pronounced. Users in muscle-building phases report this as a helpful tool for eating to a caloric surplus. The compound's appetite effect thus works with or against the user depending on their diet phase — this context-dependence should be explicitly understood before starting. No dopaminergic reward pathway activation; no psychological dependence documented. The behavioral risk is contextual rather than addictive in nature.

Prolactin elevation from GHRP-2 is moderate — documented in the Arvat 1997 study at below TRH-equivalent levels. In most users at standard doses (100 mcg, 2x daily), prolactin elevation is not clinically significant. With higher doses, higher frequencies, or individual susceptibility, prolactin can elevate enough to: cause gynecomastia (breast tissue growth in men from prolactin-mediated estrogen-relative effects), reduce libido, and reduce testosterone via prolactin suppression of GnRH. Baseline prolactin testing before starting GHRP-2 is prudent; monitoring at 4-6 weeks of use allows detection before symptoms develop. If prolactin becomes elevated: reduce dose/frequency as first intervention; if persistent, cabergoline (dopamine agonist) manages prolactin directly.

All GH secretagogues share the concern that IGF-1 elevation may be oncologically relevant. IGF-1 receptor (IGF-1R) is expressed on many tumor types and promotes cell survival and proliferation. This is not a GHRP-2-specific concern — it applies to any intervention that raises GH and downstream IGF-1. Active malignancy: contraindication. History of malignancy: physician consultation mandatory before use. The IGF-1 elevation from GHRP-2 protocols is substantially smaller than from exogenous HGH — but the theoretical concern applies at any level of IGF-1 elevation in an oncologically active context.

GHRP-2 should not be used in children or adolescents outside of formally supervised clinical settings. Manipulating the GH axis during active growth and pubertal development carries unpredictable risks to normal growth plate dynamics and endocrine development. The clinical use in GH-deficient children (Mericq 1998) was supervised, monitored, and in a pathological deficiency context — entirely different from elective performance use in a healthy adolescent.

The combination of a GHRP (GHS-R1a agonist) with a GHRH analog (GHRH receptor agonist) is the most evidence-grounded combination in GH secretagogue practice. The two pathways converge on the somatotroph: GHRH (via CJC-1295 no DAC) activates adenylate cyclase and loads secretory granules via cAMP/PKA; GHRP-2 activates PLC and triggers granule release via calcium/PKC. The combined effect is synergistic — each pathway amplifies the other's efficacy. Bowers documented 3-5x GH output vs either alone. Standard dosing: 100 mcg GHRP-2 + 100 mcg CJC-1295 (no DAC) co-injected SubQ 2-3x daily. The CJC-1295 no DAC (without the Drug Affinity Complex) produces a 30-minute GHRH-like pulse that aligns with GHRP-2's timing profile, preserving pulsatility. CJC-1295 WITH DAC has a very long half-life (days) and produces sustained GH elevation rather than pulsatile release — a different physiological pattern that the community largely avoids for the primary stack.

Ipamorelin and GHRP-2 both activate GHS-R1a — they would be competing for the same receptor site. Co-administration of two GHS-R1a agonists provides no pharmacodynamic advantage and wastes compound. The meaningful combination in GH secretagogue practice is always GHRP (GHS-R1a) + GHRH analog (GHRHR), not GHRP + GHRP. Community protocols that combine GHRP-2 with ipamorelin are pharmacologically redundant for the GH release goal.

Sermorelin is the 1-29 fragment of GHRH — the minimum active sequence for GHRH receptor binding. It activates GHRHR through the same cAMP/PKA pathway as CJC-1295 but has a shorter half-life (approximately 10-15 minutes vs CJC-1295 no DAC's 30 minutes). The GHRP-2 + sermorelin stack works through the same synergy mechanism as GHRP-2 + CJC-1295 no DAC but may require slightly more precise timing alignment. Some practitioners prefer sermorelin for its closer resemblance to physiological GHRH pulsatility.

Pre-sleep injection is the highest-priority timing for GH secretagogue use. The body's largest natural GH pulse occurs 60-90 minutes after sleep onset during slow-wave sleep. Injecting GHRP-2 + CJC-1295 30-60 minutes before sleep amplifies this natural pulse at its most biologically potent time. This timing combines: the compound's own GH-releasing effect; the natural GHRH surge associated with sleep onset; a fasted state (no recent carbohydrates); low somatostatin tone in the early sleep period. The morning fasted injection (upon waking before food) captures the next-best natural GH secretory window. Post-workout injection captures the GH-supportive post-exercise window but requires a fasted state, which conflicts with post-workout protein/carbohydrate timing for some users.

Pralmorelin (GHRP-2) received approval from Japan's Pharmaceutical and Medical Devices Agency (PMDA) in 2004 for the GHRP-2 stimulation test — a diagnostic provocative test for growth hormone deficiency. Marketed as GHRP Kaken by Kaken Pharmaceutical. This makes GHRP-2 unique among the entire GHRP family — it is the only member to have received formal regulatory approval anywhere in the world. The approval is specifically for diagnostic IV administration, not for therapeutic or performance-enhancing use. Pralmorelin is also used as a GH stimulation test in some European endocrinology centers as an alternative to the insulin tolerance test.

GHRP-2 has no FDA-approved indication in the United States. It was placed on the FDA's Category 2 bulk drug substance list (restricting 503A compounding pharmacy use) in 2023-2024 following advisory committee review. As of May 2026, while HHS has announced intent to reclassify some peptides (following the February 2026 announcement), GHRP-2 is expected to remain on Category 2 specifically because of its cortisol/prolactin elevation and appetite stimulation profile — the same characteristics that the advisory committee flagged in 2024. It remains available as a research chemical from vendors. The regulatory environment is in flux and users should track current status.

GHRP-2 (pralmorelin) is listed on the 2026 WADA Prohibited List under S2 — Peptide Hormones, Growth Factors, Related Substances and Mimetics. Prohibited at all times (in competition and out of competition). Detection: urine immunoassay (cross-reactive with anti-GH-secretagogue antibodies); LC-MS/MS for confirmatory identification and quantification. Thomas et al. (2010, Rapid Communications in Mass Spectrometry) validated the LC-MS/MS detection of pralmorelin and its metabolites in urine — the methodology for athlete testing exists and is routinely applied. Detection window: approximately 24-48 hours post-administration. Any competitive athlete in a WADA-tested sport: absolute prohibition.

• Maximum GH pulse amplitude is the priority and the cortisol co-response is acceptable: e.g., users who have confirmed low cortisol baselines, or who are taking GHRP-2 in a supervised context with baseline/monitoring labs.
• Appetite stimulation is wanted: recovery from illness, post-surgical wasting, chemotherapy-related anorexia, cachexia — all contexts where the 35.9% food intake increase documented in Laferrere 2005 is a therapeutic asset.
• Users who have established protocols with GHRP-2 and are monitoring labs showing manageable cortisol levels: no reason to switch if the profile is working.
• Combination with CJC-1295 for maximum GH synergy where cortisol management is part of the protocol: some users add phosphatidylserine (a cortisol-blunting supplement) or time GHRP-2 injections to minimize cortisol co-exposure relative to sleep timing.

• Fat loss phase where cortisol elevation directly fights against lipolysis and induces visceral fat accumulation: ipamorelin is the correct GHRP for this context.
• Users with elevated baseline cortisol (chronic stress, high-cortisol patterns): adding hCRH-equivalent cortisol stimulation on top of an already-elevated baseline creates additive HPA stress load.
• Users with sleep disruption concerns: cortisol elevation from GHRP-2 injections taken within 1-2 hours of bedtime interferes with sleep architecture. Morning-only use or ipamorelin for bedtime injection.
• Anyone who wants maximum GH benefit with minimum hormonal noise: ipamorelin has displaced GHRP-2 for this profile precisely because it provides ~70-80% of GHRP-2's GH output with essentially none of the cortisol/prolactin/appetite co-effects.

GHRP-2 and GHRP-6 are pharmacologically the most similar of the GHRP family: comparable GH output (GHRP-2 marginally higher), comparable cortisol/prolactin co-secretion, different appetite profiles. GHRP-6 produces significantly stronger appetite stimulation than GHRP-2 — this is the primary practical distinction. For users who want GHRP-class GH output with manageable hunger: GHRP-2 is preferred. For users where appetite stimulation is the feature (cachexia, underweight, difficulty eating to caloric surplus in a building phase): GHRP-6 provides stronger orexigenic effect alongside comparable GH output.

• Water retention and bloating in the first 1-2 weeks of a GHRP-2 protocol is nearly universal — consistent with GH-mediated renal water retention. Typically resolves or reduces after 2-4 weeks. Reduce carbohydrate intake and increase water intake during this phase.
• Hunger spikes 30-90 minutes after injection — reported by most GHRP-2 users; less severe than GHRP-6 but still noticeable; timing injections away from meal planning periods helps; some users take GHRP-2 immediately before an intentional meal to synchronize the hunger spike with planned eating.
• Tingling in hands/wrists, particularly upon waking — consistent with GH-mediated water retention in carpal tunnel; transient and resolves with dose reduction in most cases.
• Fatigue or increased desire to sleep after injection — consistent with ghrelin's known orexigenic/sleep-promoting effects; most pronounced with evening injections; taken as confirmation the compound is working.
• The ipamorelin migration pattern: many users who started on GHRP-2 have switched to ipamorelin after experiencing cortisol-related side effects (reduced sleep quality, fatigue despite GH elevation, difficulty cutting fat). Community consensus: ipamorelin for most goals; GHRP-2 for maximum GH amplitude or appetite support.

GHRP-2 is a small hexapeptide (MW 817.97 Da) — relatively straightforward to synthesize and sequence-verify. HPLC purity testing establishes absence of major impurities; mass spectrometry confirms sequence identity. The primary quality concern for GHRP-2 research chemical is accurate concentration — underdosing is more common than misdosing in this product category. Endotoxin testing is important for any injectable peptide. Standard peptide sourcing principles apply: require HPLC + MS COA, check endotoxin limits, verify lyophilized (not pre-reconstituted) presentation for stability. GHRP-2 is stable as lyophilized powder; reconstituted solution should be refrigerated and used within 4 weeks.

• Exceeding 100 mcg per injection: the GH response is saturated at ~100 mcg. More compound means more cortisol and prolactin, not more GH. The saturation dose is the optimal dose.
• Injecting after carbohydrate-containing meals: insulin blunts the GH response substantially. Fast for 2-3 hours before injection, especially the pre-sleep dose.
• Daily forever without cycling: partial desensitization reduces GH output over time with continuous daily use. 8-12 week cycles with 4-6 week breaks maintain receptor sensitivity.
• Combining with another GHS-R1a agonist (GHRP-6, ipamorelin): receptor competition wastes compound. The synergistic combination is GHRP (GHS-R1a) + GHRH analog (GHRHR), not two GHRPs.
• Ignoring the cortisol effect: baseline and on-cycle cortisol monitoring allows detection of problematic cumulative HPA activation before it becomes symptomatic.

Bowers CY, Reynolds GA, Durham D, Barrera CM, Pezzoli SS, Thorner MO. (1990). Growth hormone (GH)-releasing peptide stimulates GH release in normal men and acts synergistically with GH-releasing hormone. Journal of Clinical Endocrinology and Metabolism. 70(4):975-982. [Original human confirmation; GH stimulation; GHRH synergy demonstrated.]

Arvat E, Maccagno B, Broglio F, Boghen MF, Deghenghi R, Camanni F, Ghigo E. (1997). Endocrine activities of pralmorelin (KP-102/GHRP-2) and hexarelin in humans: dose-response study. Eur J Endocrinol. 136(4):369-74. [The definitive human pharmacology study: GH, cortisol, ACTH, prolactin dose-response; ACTH/cortisol response comparable to hCRH; prolactin measurable.]

Laferrere B, Abraham C, Russell CD, Bowers CY. (2005). Growth hormone releasing peptide-2 (GHRP-2), like ghrelin, increases food intake in healthy men. Journal of Clinical Endocrinology and Metabolism. 90(2):611-614. PMID 15699539. [n=7; GHRP-2 infusion produced 35.9% ± 10.9% increase in ad libitum food intake; confirmed ghrelin-like appetite effect in humans.]

Chihara K, Sugimoto Y, Shimatsu A, Tanaka T, et al. (2007). A simple diagnostic test using GH-releasing peptide-2 in adult GH deficiency. European Journal of Endocrinology. 157(1):19-27. [Validation of GHRP-2 stimulation test for GH deficiency diagnosis; comparison to ITT; basis for Japan PMDA approval.]

Mericq V, Bowers CY, Mejia G, Patiño L, Avila A. (1998). Increased GH and IGF-1 responses to GHRP-2 in GH-deficient children. [8-month study; stepwise dose escalation; IGF-1 elevation; proof-of-concept for GH deficiency treatment.]

Howard AD, Feighner SD, Cully DF et al. (1996). A receptor in pituitary and hypothalamus that functions in growth hormone release. Science. 273(5277):974-977. [Discovery of GHS-R1a — the receptor GHRP-2 acts on; orphan receptor characterization.]

Kojima M, Hosoda H, Date Y et al. (1999). Ghrelin is a growth-hormone-releasing acylated peptide from stomach. Nature. 402(6762):656-660. [Discovery of ghrelin — the endogenous ligand for GHS-R1a; identified 15 years after GHRPs were developed.]

Synthetic Growth Hormone-Releasing Peptides (GHRPs): A Historical Appraisal of the Evidences Supporting Their Cytoprotective Effects. (2017). PMC5392015. [Review of GHRP cytoprotection via CD36 + GHS-R1a; cardiac, hepatic, neural protection in preclinical models; GH-independent mechanisms.]

Thomas A, Kohler M, Schänzer W, Thevis M. (2010). Determination of growth hormone secretagogue pralmorelin (GHRP-2) and its metabolite in human urine by LC-MS/MS. Rapid Communications in Mass Spectrometry. 24(11):1549-1557. [WADA anti-doping detection methodology; validated urine testing for pralmorelin and metabolites.]

• Well-suited for: users who want maximum GH pulse amplitude from the GHRP class and accept the cortisol trade-off with monitoring; users needing appetite stimulation alongside GH support; clinical GH deficiency diagnostic use (Japan/professional context only).
• Poorly suited for: fat-loss phases (cortisol and appetite stimulation fight caloric restriction); users with high-baseline cortisol; users prioritizing clean hormonal profile; athletes in tested sports (WADA S2 absolute prohibition).
• Better choice for most goals: ipamorelin + CJC-1295 (no DAC) provides ~70-80% of GHRP-2's GH pulse output without meaningful cortisol, prolactin, or appetite co-effects. This combination has displaced the GHRP-2 equivalent stack in community practice for a pharmacologically sound reason.

• 'More compound = more GH': false above 100 mcg. The dose-response is saturated at ~100 mcg. Doses above this add cortisol and prolactin but not GH.
• 'GHRPs can be combined for stronger GH': two GHS-R1a agonists compete for the same receptor. The synergy is GHRP + GHRH analog — two different receptors. Stacking GHRP-2 with ipamorelin is pharmacologically redundant.
• 'Japan approval means FDA approval': Japan's pralmorelin approval is for a specific diagnostic test, IV-administered, in GH-deficient patients under physician supervision. It does not validate therapeutic or performance-enhancing use and has no bearing on FDA status.

— End of GHRP-2 —

THE PEPTIDE BIBLE | GHRP-2 | For Research & Educational Purposes Only