GHRP-2
A first-generation synthetic hexapeptide ghrelin-receptor agonist that drives potent pulsatile growth hormone release, at the cost of modest cortisol, prolactin, and appetite stimulation.
GHRP-2 is a synthetic hexapeptide growth hormone secretagogue (sequence D-Ala-D-2Nal-Ala-Trp-D-Phe-Lys-NH2) that binds the ghrelin receptor (GHS-R1a) on pituitary somatotrophs and hypothalamic neurons to stimulate dose-dependent GH release. Developed from Cyril Bowers' foundational work at Tulane University in the late 1980s and 1990s, it is approved in Japan as pralmorelin for diagnostic GH-deficiency testing but is not FDA-approved for any therapeutic indication. It produces a stronger GH pulse than GHRP-6 with less appetite stimulation, but its non-selective co-elevation of cortisol and prolactin has led most modern GH-axis protocols to favor the cleaner successor, ipamorelin.
Class
Synthetic hexapeptide (ghrelin/GHS-R1a receptor agonist, GH secretagogue)
Half-life
Approximately 15-60 minutes (short-acting pulsatile effect)
Routes
Subcutaneous, Intramuscular, Intranasal, Intravenous (diagnostic testing)
Category
Growth Hormone & Performance
Researched benefits
What it's studied for
Potent pulsatile GH release
GHRP-2 stimulates strong, reliable, dose-dependent growth hormone release from pituitary somatotrophs via GHS-R1a agonism, producing a GH pulse larger in peak amplitude than GHRH alone. The effect is robust enough that it is used clinically as a diagnostic provocation test for GH deficiency.
Downstream IGF-1 elevation for body composition
The GH pulse drives increased IGF-1, which community and research use targets for muscle building, recovery, and improved body composition. IGF-1 typically stabilizes at a new elevated setpoint around weeks 4-6 of consistent dosing.
Synergy with GHRH analogs
GHRP-2's most significant pharmacological property is profound synergy with GHRH analogs such as sermorelin, CJC-1295, and tesamorelin; the ghrelin (Gq/11) and GHRH (Gs/cAMP) pathways converge intracellularly to amplify GH pulse amplitude 3-5x above either compound alone (Bowers et al., 1991).
Appetite stimulation
As a ghrelin-receptor agonist, GHRP-2 measurably increases appetite within 30-60 minutes of injection. This is advantageous for users in caloric surplus (bulking, recovery from illness) though counterproductive during a deficit; the effect is stronger than ipamorelin but less than GHRP-6 or oral MK-677.
Validated diagnostic GH-stimulation agent
GHRP-2 (pralmorelin) is an established, clinically validated provocation agent for assessing somatotropic axis integrity, replacing older insulin-tolerance protocols in Japan due to its superior safety and more reliable GH response.
Improved sleep and recovery
Bedtime dosing aligns with the dominant nocturnal GH pulse; users commonly report vivid dreams and enhanced slow-wave sleep within the first two weeks, alongside subjective recovery and training-tolerance improvements within 2-3 weeks.
Mechanism
How it works
GHRP-2 binds the growth hormone secretagogue receptor type 1a (GHS-R1a) — the endogenous target of ghrelin — with nanomolar affinity. This receptor is expressed on anterior pituitary somatotrophs (driving direct GH release), on hypothalamic arcuate nucleus neurons (NPY/AgRP and GHRH neurons, providing indirect amplification), on pituitary lactotrophs (a weak prolactin-releasing signal), and indirectly influences the adrenal cortex via HPA stimulation (a weak cortisol effect).
At the somatotroph, GHS-R1a activation couples through Gq/11 to phospholipase C, generating IP3 and triggering intracellular calcium release, which drives GH granule exocytosis within minutes. Simultaneously, GHRP-2 enhances GHRH neuronal output from the arcuate nucleus and antagonizes somatostatin tone at the hypothalamic level, effectively lifting the inhibitory ceiling that limits GHRH. The result is a GH pulse larger in peak amplitude and longer in duration than GHRH alone can produce.
This dual action explains the compound's hallmark synergy with GHRH analogs: GHRH receptor activation raises cAMP via Gs while GHS-R1a activation raises IP3/calcium via Gq/11, and the combined signaling amplifies GH release 3-5x above either mechanism alone. It also explains the non-selective profile — residual activity at MC2R-adjacent pathways and lactotroph spillover produce the modest cortisol (roughly +15-25% above baseline) and prolactin elevations that distinguish GHRP-2 from the more selective ipamorelin.
Because it is a ghrelin mimetic, GHRP-2 inherently stimulates hunger, GH release, cortisol, and prolactin from the same receptor engagement. The short 15-60 minute half-life makes its action pulsatile, closely mimicking natural GH secretion patterns, which is why it is dosed as multiple small injections timed to fasted windows when GH release is not blunted by insulin-driven somatostatin tone.
Dosing protocols
Dosing & administration
Dosing reflects protocols reported in research and community literature for educational purposes. It is not medical advice or a recommendation. Most peptides here are not approved for human use.
Reconstitution
GHRP-2 ships as a white lyophilized powder, typically in 5 mg or 10 mg vials. Reconstitute a 5 mg vial with 2 mL of bacteriostatic water for a 2.5 mg/mL concentration (100 mcg = 0.04 mL = 4 units on a U-100 insulin syringe; 150 mcg = 6 units; 200 mcg = 8 units; 300 mcg = 12 units). Direct the water down the inside wall rather than onto the powder cake, do not shake — gently swirl or roll for 30-60 seconds until clear and colorless. A higher-concentration alternative is 5 mg + 1 mL (5 mg/mL, so 100 mcg = 2 units) but the smaller volume is harder to measure accurately. Store lyophilized vials refrigerated at 2-8°C (stable up to 2 years); use reconstituted solution within 30 days, never freeze it, and protect from light.
Beginner
- Dose
- 100 mcg per injection (200 mcg/day total)
- Frequency
- 2x daily
- Timing
- Fasted, empty-stomach windows — pre-breakfast and pre-bed
- Duration
- 12-16 weeks to assess response
- Route
- Subcutaneous
Most users tolerate 100 mcg SC without appreciable nausea or flushing; a mild warm head-rush in the first 5 minutes fades quickly. Appetite increase is noticeable within an hour. Run baseline IGF-1, fasting insulin/glucose, HbA1c, and AM cortisol before starting.
Intermediate
- Dose
- 100-200 mcg per injection (300-450 mcg/day total)
- Frequency
- 3x daily
- Timing
- Fasted — pre-breakfast, pre-training, pre-bed
- Duration
- 12-week cycles
- Route
- Subcutaneous
Commonly combined with a GHRH analog: GHRP-2 150-200 mcg plus sermorelin 200-300 mcg or CJC-1295 (no-DAC) 100-200 mcg, both drawn into the same syringe and injected together for 3-5x GH amplification. Consider 5-on/2-off weekly or 8-week-on/2-week-off cycling to preserve receptor sensitivity.
Advanced
- Dose
- 150-200 mcg per injection (450-600 mcg/day total)
- Frequency
- 3x daily
- Timing
- Fasted — pre-breakfast, pre-training, pre-bed
- Duration
- 8-12 week aggressive anabolic phases
- Route
- Subcutaneous
Reserved for short-duration phases where maximum GH pulse amplitude matters more than cortisol/prolactin cleanliness, or bulking where appetite stimulation is desired. Doses beyond 200 mcg per injection show diminishing returns due to GHS-R1a saturation. Many advanced users instead transition to ipamorelin for cleaner long-term use.
Diagnostic (Japan)
- Dose
- 0.3-1 mcg/kg
- Frequency
- Single bolus
- Timing
- Controlled clinical setting
- Duration
- Single provocation test
- Route
- Intravenous
Used as a validated GH-stimulation (provocation) test for GH deficiency; the IV route is reserved for this diagnostic context.
- Always dose fasted — wait at least 2-3 hours after the last meal. Elevated glucose and insulin blunt GH release by increasing somatostatin tone, meaningfully reducing GHRP-2 potency.
- Single-injection ceiling is roughly 300 mcg; above this, GHS-R1a receptor saturation prevents additional GH release. Increasing frequency beyond 3x daily gives more consistent GH elevation but does not raise total output much.
- Weight-based guidance is roughly 1-2 mcg/kg per injection, with a saturation dose near 100-200 mcg for most users.
- Consistency of timing matters — the GH axis entrains to regular schedules, and variability reduces effectiveness.
- Cycle to preserve receptor sensitivity: common approaches are 5 days on/2 off weekly, or 8 weeks on/2 weeks off. Target IGF-1 in the upper quartile of the age-adjusted range, not supraphysiologic.
- Monitor IGF-1 and fasting glucose at week 8, a full panel (including cortisol and prolactin) at week 16, then IGF-1 plus fasting glucose every 3 months.
- Discontinue for persistent joint pain, carpal tunnel symptoms, peripheral edema, persistently elevated fasting glucose (>110 mg/dL), cushingoid changes, worsening sleep apnea, or any cardiovascular symptoms.
Evidence
Research & clinical studies (2)
Preoperative growth hormone (GH) peak values during a GH releasing peptide-2 test reflect the severity of hypopituitarism and the postoperative recovery of GH secretion in patients with non-functioning pituitary adenomas
In 76 patients with non-functioning pituitary adenomas, preoperative GHRP-2 stimulation test peak GH values correlated with the severity of anterior pituitary hormone deficiency and predicted postoperative recovery of GH secretion, validating GHRP-2 as a sensitive diagnostic tool for somatotropic axis integrity.
PMID 31776295Adult growth hormone deficiency: current concepts
This review notes that the GHRP-2 stimulation test reliably evaluates GH secretory capacity in adults and that GH replacement therapy improves body composition, dyslipidemia, and quality of life in deficient patients.
PMID 25070016Combinations
Stacking & blends
GHRP-2 + CJC-1295 (no-DAC)
Maximal synergistic GH pulse for body composition and recovery
GHRP-2 activates the ghrelin/GHS-R1a pathway while CJC-1295 activates the GHRH pathway; the two converge intracellularly to amplify GH pulse amplitude 3-5x above either alone. Standard stack is 100-200 mcg of each drawn into the same insulin syringe and injected SC 2-3x daily fasted.
Sermorelin + GHRP-2: GH Stimulation & Recovery
Amplify natural GH release for muscle growth, fat loss, and anti-aging
A GHRH analog (sermorelin) plus a ghrelin-mimetic GHRP activates two distinct receptor pathways to synergistically boost endogenous GH; commonly researched for body composition, recovery, and age-related GH decline. Typical pairing is GHRP-2 150-200 mcg with sermorelin 200-300 mcg SC.
Full performance / anabolic stack
8-12 week aggressive anabolic and recovery phase
GHRP-2 (200 mcg x3 daily) with CJC-1295 no-DAC (100 mcg x3 daily) maximizes the GH pulse, while BPC-157 (500 mcg x2 daily) and TB-500 (2 mg x2 weekly) support connective tissue and soft-tissue remodeling for training recovery.
GHRP-2 + Testosterone Replacement
Additive body composition improvement
Well-established anabolic synergy between GH-axis stimulation and androgen replacement produces additive effects on lean mass and body composition.
Safety
Side effects & considerations
Commonly reported effects
Contraindications & cautions
- Active malignancy, particularly hormone-responsive cancers (breast, prostate) where elevated IGF-1 may promote tumor growth
- Strong family history of GH-axis-sensitive cancers (requires specialist supervision)
- Pregnancy and lactation (no established safety data)
- Known hypersensitivity to GHRP-2 or related hexapeptides
- Severe untreated obstructive sleep apnea
- Acute critical illness (sepsis, major trauma, respiratory failure, post-surgical recovery)
- Diabetic ketoacidosis or severe uncontrolled diabetes
- Active proliferative retinopathy
- Prolactinoma or hyperprolactinemia
- Cushing's syndrome or baseline elevated cortisol
- Adrenal insufficiency with hypothalamic-pituitary disease
GHRP-2's defining safety consideration versus more selective secretagogues is its non-selective co-stimulation of cortisol and prolactin — modest and clinically trivial in short-term or intermittent use, but relevant with chronic daily dosing, especially for users with baseline anxiety, HPA-axis dysregulation, or prolactin issues, who often do better on ipamorelin. Chronic use can cause modest insulin resistance and GHS-R1a receptor desensitization, both mitigated by cycling. Use caution with corticosteroids (reduced GH response and altered glucocorticoid regulation), opioids (may augment cortisol/prolactin effects), and thyroid hormone. Combining with exogenous HGH is pointless, and combination with GLP-1 agonists partially antagonizes their appetite suppression. Long-term safety at sustained research-use dosing is not well characterized given the absence of completed long-duration trials.
FAQ
GHRP-2 — common questions
How is GHRP-2 different from GHRP-6?
Both are hexapeptide ghrelin-receptor agonists, but GHRP-2 produces a stronger GH response with much less appetite stimulation. GHRP-6 binds the hypothalamic appetite-related ghrelin pathways more strongly, so buyers seeking GH release without significant hunger generally prefer GHRP-2.
How does GHRP-2 compare to ipamorelin?
Both target GHS-R1a, but GHRP-2 produces a larger absolute GH pulse while also modestly elevating cortisol (about +15-25%), prolactin, and appetite. Ipamorelin is more selective with minimal cortisol/prolactin changes. GHRP-2 suits short-duration aggressive phases or bulking where appetite is a bonus; ipamorelin is preferred for clean long-term daily use or cutting.
What is the best GHRP-2 dosage?
The standard subcutaneous protocol is 100-200 mcg per injection, 2-3 times daily. Beginners start at 100 mcg twice daily (pre-breakfast and pre-bed) and titrate up; intermediate users dose 150-200 mcg three times daily. The single-injection ceiling is around 300 mcg — above that receptor saturation prevents extra GH release. Always dose fasted, 2-3 hours after eating.
Can GHRP-2 be combined with CJC-1295?
Yes — this is the classical GH-secretagogue stack. GHRP-2 works through the ghrelin/GHS-R1a pathway and CJC-1295 through the GHRH pathway; the two converge intracellularly to amplify GH pulse amplitude 3-5x above either alone. Standard stack: GHRP-2 100-200 mcg plus CJC-1295 no-DAC 100-200 mcg in the same syringe, SC 2-3x daily fasted.
Is GHRP-2 FDA-approved or legal?
GHRP-2 (pralmorelin) is approved in Japan as a diagnostic agent for GH-deficiency testing but is not FDA-approved for any indication in the US, where it is sold under research-only classification. It is on the WADA Prohibited List (S2) for competitive athletes.
Does GHRP-2 cause weight gain?
It can cause modest weight gain through appetite stimulation (measurable hunger within 30-60 minutes) if met with caloric surplus, plus mild fluid retention in the first 2-3 weeks. On maintenance or a deficit, body composition typically shifts toward slightly more lean mass with modest scale change. For weight loss, ipamorelin's weaker appetite effect is usually better.
How long does it take GHRP-2 to work?
A single injection raises GH within minutes, peaking around 15-30 minutes and returning to baseline by 90-120 minutes. Body composition and performance effects take 8-16 weeks of consistent dosing; IGF-1 stabilizes around weeks 4-6, sleep improvements often appear within 2 weeks, and lean mass changes are detectable at weeks 8-12.
Should I cycle GHRP-2?
Cycling is recommended for long-term use because chronic GHS-R1a stimulation can cause modest receptor desensitization. Common approaches are 5 days on/2 off weekly, or 8 weeks on/2 weeks off. Peptide cycling here is about maintaining receptor sensitivity rather than protecting endogenous hormone production, which recovers quickly.
