GHRP-2

Plain-English version: GHRP-2 is a tiny lab-made protein fragment — just six amino acids long — that acts like a "release" button for your body's own growth hormone. Instead of putting GH into your body from the outside, it signals the pituitary gland (a pea-sized gland at the base of the brain) to fire off a natural pulse of GH.

Its amino-acid sequence is D-Ala-D-2-Nal-Ala-Trp-D-Phe-Lys-NH2. "GHRP" stands for Growth Hormone Releasing Peptide, and "2" marks it as the second in a numbered series. It is also known by the drug name pralmorelin and the research code KP-102 (or GHRP Kaken 100 in Japan).

GHRP-2 traces back to the pioneering work of Cyril Bowers at Tulane University. In the early 1980s, Bowers and colleagues discovered that certain modified peptides could specifically stimulate GH release from pituitary cells through a pathway completely separate from the then-known GHRH/somatostatin system.^[1] That work opened an entirely new branch of endocrinology and launched the growth-hormone-secretagogue drug class.^[9] The receptor these peptides activated was, at the time, an "orphan" — a lock with no known key. Hunting for that key is what led a Japanese team in 1999 to discover ghrelin, the natural stomach hormone that GHRPs mimic.^[2] In other words, synthetic GHRPs like GHRP-2 came before science even knew the natural hormone they were copying.

The credibility picture, stated up front: GHRP-2 has more human data than most research peptides, but it is a specific kind of data. Its one regulatory approval — in Japan, as pralmorelin — is for a single-dose diagnostic test for growth-hormone deficiency, not for ongoing treatment.^[8] It has never been approved by the U.S. FDA for any indication, it is sold only as a research chemical (it is not a dietary supplement), and it is prohibited in sport by the World Anti-Doping Agency. No study has ever tracked the long-term safety of people self-administering it for months or years.

Takeaway first: GHRP-2 binds the ghrelin receptor (GHSR-1a) on the pituitary and triggers a GH pulse. That is its main job. But the same receptor sits in other places too, which is why GHRP-2 also nudges cortisol, prolactin, and appetite — it is powerful, but it is not surgically selective.

1. GH release through the ghrelin receptor (the main event)

GHRP-2 activates GHSR-1a on pituitary somatotrophs (the GH-producing cells). This works through a phospholipase-C / IP3 / calcium-influx pathway that depolarizes the cell and drives it to dump growth hormone. Because it mimics ghrelin, it is a genuine ghrelin-receptor agonist — the same lock the stomach's own hunger hormone opens.^[2] Head-to-head human work shows that ghrelin-type peptidyl secretagogues release far more GH than GHRH does on its own.^[3]

2. Synergy with GHRH (why people stack it)

Growth-hormone-releasing hormone (GHRH) — and its analogs CJC-1295 and sermorelin — works through a different internal switch (a cAMP/PKA pathway). Because GHRP-2 and GHRH pull two separate levers, giving them together produces a GH pulse larger than the sum of either alone. In seven healthy men, co-administering a ghrelin-type secretagogue with GHRH produced a clearly synergistic GH release.^[3] This is the mechanistic reason the "GHRP + GHRH" stack is the standard approach in GH-optimization research.

3. Cortisol and prolactin (the selectivity cost)

This is the honest downside. In a direct human study, GHRP-2 given intravenously at 1–2 mcg/kg to both young and elderly adults raised not only GH but also prolactin, ACTH, and cortisol.^[4] ACTH is the hormone that tells the adrenal glands to make cortisol, so the cortisol rise follows the ACTH rise. This is exactly why GHRP-2 is described as "less clean" than ipamorelin, which was specifically engineered to release GH without much cortisol or prolactin. The effect is dose-dependent, so it matters more at higher doses and with more frequent dosing.

4. Appetite stimulation

Because ghrelin is the body's hunger hormone, activating its receptor makes you hungry. In a controlled study of lean healthy men, a GHRP-2 infusion increased food intake by about 36% versus placebo, with more reported pre-meal hunger.^[7] That is a meaningful, measured effect — useful if you are trying to eat more during a bulk, counterproductive if you are trying to lose fat.

What we do NOT know

There is no long-term human pharmacokinetic or safety profile for repeated self-dosing. The mechanisms above are real, human-verified findings — but most come from acute (single-dose or short-infusion) studies. How the cortisol and prolactin picture behaves over months of daily use in a healthy person chasing body composition is genuinely unstudied.

How to read this section: for each area we give the plain-English claim, the proposed mechanism, the population actually studied, the observed effect, and the limitation. GHRP-2 has better human data than most peptides — but note whether each finding comes from a diagnostic test, an acute study, or the single 30-day trial.

Potent, sustained growth-hormone release

Claim: GHRP-2 reliably and strongly raises growth hormone. Mechanism: ghrelin-receptor (GHSR-1a) activation on pituitary somatotrophs. Population: healthy older men and women in a 30-day continuous subcutaneous infusion study; separately, controls and GH-deficient patients in the diagnostic validation. Effect: a 30-day continuous infusion (1 mcg/kg/hour) raised pulsatile GH more than 3-fold on day 1 and roughly 1.8-fold on days 14 and 30, and sustained elevated IGF-1, IGFBP-3, and IGFBP-5 the whole time.^[6] That last point matters: the effect did not fully "burn out," which is the evidence behind GHRP-2's reputation for minimal desensitization. In the diagnostic setting, a single 100 mcg IV dose drove peak GH to about 84.6 mcg/L in healthy controls.^[8] Limitation: the 30-day study used continuous infusion in older adults, not the intermittent subcutaneous injections hobbyists use, and both studies measured hormones — not real-world outcomes like muscle gained.

Synergy with GHRH analogs

Claim: pairing GHRP-2 with a GHRH analog produces a bigger GH pulse than either alone. Mechanism: the two act through complementary intracellular pathways (calcium-driven vs. cAMP-driven). Population: healthy men. Effect: co-administration of a ghrelin-type secretagogue with GHRH produced clearly synergistic GH output.^[3] Limitation: demonstrated acutely; long-term body-composition outcomes of the stack are not trial-proven.

Documented efficacy in growth-deficient patients

Claim: GHRP-2 can meaningfully drive growth in people who lack GH. Mechanism: stimulated endogenous GH secretion. Population: 15 children with short stature, given intranasal GHRP-2 (5–15 mcg/kg). Effect: growth velocity rose from 3.7 to 6.1 cm/year at 6 months and was sustained at 18–24 months, with good tolerability.^[5] Limitation: this is a small pediatric study in short-stature children — it validates that GHRP-2 raises GH enough to change a real outcome, but it does not translate directly to healthy adults using it for physique or anti-aging.

Appetite and body composition

Claim: GHRP-2 increases appetite and, via GH, supports fat metabolism and lean-mass goals. Mechanism: ghrelin-mimetic hunger signaling plus GH-driven lipolysis. Population: seven lean healthy men. Effect: a subcutaneous infusion (1 mcg/kg/hour) increased food intake by 35.9% versus placebo.^[7] Elevated GH itself promotes fat breakdown and lean-tissue support, so the body-composition rationale is real — but the appetite bump can work against a fat-loss goal and in favor of a bulk. Limitation: the measured outcome here is appetite, not long-term fat or muscle change; the physique benefits are extrapolated from GH physiology, not from a GHRP-2 body-composition trial.

The honest bottom line on "benefits"

• GHRP-2 clearly raises GH in humans — that part is well established across diagnostic, acute, and 30-day studies.^[6][8]
• The leap from "raises GH" to "builds muscle / reverses aging in healthy adults" is not proven by a controlled trial. That inference rests on GH physiology, not on a GHRP-2 physique study.
• Appetite stimulation is a real, measured effect — plan your goal around it.^[7]
• Long-term outcomes and safety of repeated self-dosing are simply unstudied.

Read this first: there is no approved therapeutic dose of GHRP-2 for healthy adults. The only officially sanctioned protocol is Japan's single 100 mcg IV diagnostic dose.^[8] The research-community doses below come from convention and from human study parameters (e.g., the 1 mcg/kg/hour infusion rate used in trials^[6][7]), not from a trial that validated a subcutaneous physique-optimization regimen. We describe them for completeness and harm reduction, not as medical guidance.

Commonly referenced research protocols (not validated for physique use)

Protocol	Dose	Frequency	Notes
Standalone	100–300 mcg	1–3× daily	Subcutaneous, fasted
With CJC-1295 (no DAC)	100–200 mcg GHRP-2 + 100–200 mcg CJC	1–3× daily	Can be drawn in the same syringe, SC
With sermorelin	100–200 mcg GHRP-2 + ~200 mcg sermorelin	Before bed	SC, fasted
Diagnostic (Japan, approved)	100 mcg	Single dose	Intravenous, clinician-administered

The "saturation dose" idea in plain terms: the ghrelin receptor has a ceiling. Past roughly 100 mcg per injection, adding more GHRP-2 yields diminishing extra GH, so many protocols favor more frequent ~100 mcg doses over a few very large ones. This also helps limit the cortisol and prolactin creep that comes with bigger doses.^[4]

Timing (why fasted matters)

• Empty stomach is important. Food — especially carbohydrates and fats — raises somatostatin and insulin, which blunt the GH response. Wait at least 2 hours after eating, and ideally 20–30 minutes before your next meal.
• Best windows: on waking (fasted), post-workout (if fasted), and before bed. The bedtime dose is often considered most valuable because it amplifies the body's natural nighttime GH pulse.
• Appetite note: because GHRP-2 makes you hungry within 20–30 minutes,^[7] a pre-meal dose can conveniently double as an appetite primer during a bulk.

Reconstitution math, with a worked example

GHRP-2 ships as a lyophilized (freeze-dried) powder that must be mixed with bacteriostatic water before use. The core formula:

Concentration (mg/mL) = vial amount (mg) ÷ water added (mL)

Worked example: take a 5 mg vial and add 2 mL of bacteriostatic water. That gives 5 ÷ 2 = 2.5 mg/mL, i.e. 2,500 mcg per mL. To draw a 100 mcg dose: 100 ÷ 2,500 = 0.04 mL, which is 4 units on a standard 100-unit insulin syringe. A 200 mcg dose is 0.08 mL, or 8 units.

Vial	BAC water	Concentration	100 mcg	200 mcg
5 mg	2 mL	2.5 mg/mL	0.04 mL (4 units)	0.08 mL (8 units)
5 mg	1 mL	5.0 mg/mL	0.02 mL (2 units)	0.04 mL (4 units)
2 mg	1 mL	2.0 mg/mL	0.05 mL (5 units)	0.10 mL (10 units)

Preparation steps: wipe the stopper with alcohol; inject the water slowly down the inside wall of the vial rather than blasting the powder; swirl gently (do not shake) until fully dissolved; label the vial with the date and concentration. Use the peptide calculator and bacteriostatic water calculator to check volumes, and the reconstitution guide for a full walkthrough.

Cycle length and stacking rules

• Desensitization is minimal. Unlike hexarelin, GHRP-2 sustained its effect across a 30-day continuous infusion without fully burning out,^[6] so it does not need aggressive cycling to keep working. Many protocols still run 8–12 weeks with periodic breaks to let cortisol and prolactin normalize.
• Do not stack two GHRPs. Combining GHRP-2 with GHRP-6 or hexarelin is pointless — they compete for the same receptor. Pair a GHRP with a GHRH analog instead.
• Storage: lyophilized vials are stable at room temperature for weeks and refrigerated for months. Once reconstituted, store at 2–8°C and use within about 4 weeks; discard anything cloudy or discolored.

None of this is a recommendation to self-administer an unapproved compound — it describes how the research doses are structured.

Straight talk: GHRP-2's defining safety issue is that it is not a selective GH releaser. Human studies confirm it raises prolactin, ACTH, and cortisol alongside GH,^[4] and it reliably increases appetite.^[7] Its acute and diagnostic use has been well tolerated,^[5][8] but there are no controlled long-term safety trials of repeated self-dosing.

Reported effects, grouped by how often they show up

Effect	Frequency	Severity	Notes
Increased appetite / hunger	Common	Mild–moderate	Measured ~36% rise in food intake; onset 20–30 min[7]
Flushing / warmth after injection	Common	Mild	Usually lasts 5–10 minutes
Tingling / pins-and-needles	Common	Mild	Transient, around injection time
Water retention / mild puffiness	Occasional	Mild	GH-mediated; often in hands/feet
Injection-site redness or itching	Occasional	Mild	Typical of subcutaneous injections
Elevated cortisol	Dose-dependent	Variable	More pronounced at higher/more frequent doses[4]
Elevated prolactin	Dose-dependent	Variable	Can affect libido, mood, nipple sensitivity[4]
Carpal-tunnel-type numbness	Rare	Mild–moderate	Associated with sustained high GH

Why the cortisol and prolactin matter

These are the two effects that separate GHRP-2 from cleaner options. Chronically elevated cortisol can promote fat storage (especially visceral), blunt immune function, and disrupt sleep — partially working against the very body-composition goals people take GHRP-2 for. Elevated prolactin can reduce libido, affect mood, and in men contribute to nipple sensitivity; in women it can disturb menstrual regularity. Both effects are dose-dependent,^[4] which is the practical argument for keeping per-injection doses near the ~100 mcg saturation point and monitoring bloodwork on longer runs.

Who should avoid it (theoretical and precautionary)

• Prolactin-sensitive conditions (e.g. existing hyperprolactinemia) — GHRP-2's prolactin rise is a direct concern.
• Cortisol-related disorders (e.g. Cushing's syndrome) — added ACTH/cortisol stimulation is unwanted.
• Active or recent cancer — raising GH/IGF-1 is generally considered off-limits until specifically studied, because IGF-1 is a growth signal.
• Pregnancy and breastfeeding — no reproductive-safety data; avoid.
• Diabetes or insulin resistance — GH can raise blood glucose and reduce insulin sensitivity; medical oversight is warranted.

The limitations you must keep in mind

• Most human data are acute (single-dose or short-infusion) or diagnostic — not long-term.
• The off-target cortisol and prolactin effects are established in humans, not merely theoretical.^[4]
• Product quality varies in the unregulated research market — contaminants can cause effects wrongly blamed on the peptide.

For broader context, see Are Peptides Safe? and Peptide Side Effects.

Choosing among GH secretagogues means trading raw potency against selectivity. GHRP-2 sits at the high-potency, lower-selectivity end.

Feature	GHRP-2	Ipamorelin	GHRP-6	Hexarelin
GH release potency	Highest	Moderate	High	Very high
Cortisol increase	Moderate	Minimal	Significant	Moderate
Prolactin increase	Significant	Minimal	Moderate	Moderate
Appetite stimulation	Moderate	Minimal	Intense	Moderate
Desensitization	Minimal	Minimal	Minimal	Significant
Regulatory status	Approved (Japan, diagnostic only)	Research only	Research only	Research only

How to choose: for most GH-optimization goals, ipamorelin is preferred for its clean side-effect profile. GHRP-2 is chosen when maximum GH output is the priority and the user is prepared to manage cortisol and prolactin. GHRP-6 is picked specifically when intense appetite stimulation is wanted (hardgainers). Hexarelin is the most potent but desensitizes with chronic use. See the full GHRP-2 vs GHRP-6 comparison for a deeper dive.

Why this section matters: GHRP-2 is sold as an unregulated research chemical, so purity and identity vary a lot between suppliers. For an unapproved peptide you may inject, contamination can be a bigger practical risk than the peptide itself. Knowing how to read a Certificate of Analysis (COA) is the single most useful skill here.

What a credible product should show

• Third-party COA: independent HPLC purity testing (look for ≥98%) plus mass-spectrometry identity confirming the expected molecular weight for the GHRP-2 sequence.
• Batch-specific results: the COA should reference the exact lot you are buying, not a generic sample.
• Endotoxin testing (LAL): important for anything intended to be injected.
• Proper form and packaging: lyophilized powder in a sealed, light-protected vial — not a pre-mixed "ready to use" liquid.

Red flags

• No COA, or a COA from the seller rather than an independent lab
• Pre-mixed liquid peptide (shorter shelf life, higher contamination risk)
• Prices far below the market
• Explicit human-use or medical claims, which signal a non-compliant, higher-risk vendor

Legal and regulatory status (2026)

• Not FDA-approved for any therapeutic use, in the U.S. or elsewhere. It is sold only as a research chemical and is not a dietary supplement.
• Approved in Japan as pralmorelin (GHRP Kaken 100) — but strictly as a single-dose diagnostic agent for growth-hormone deficiency, not as a treatment.^[8]
• Banned in sport: prohibited by WADA under class S2 (peptide hormones, growth factors). GHRP-2 and its metabolites are detectable in urine, so competitive athletes should treat it as bannable.
• Not a controlled substance: GHRP-2 is not DEA-scheduled.

Storage

Keep unopened lyophilized vials cold and dark (refrigerator or freezer). Once reconstituted, refrigerate at 2–8°C and use within about 4 weeks; never freeze a reconstituted solution, and discard anything cloudy or discolored. See the full peptide storage guide. For the complete legal picture, read Are Peptides Legal?