GHRP-6
The original ghrelin-receptor GH secretagogue, distinguished by the strongest appetite stimulation of the GHRP class.
GHRP-6 is a synthetic hexapeptide (His-D-Trp-Ala-Trp-D-Phe-Lys-NH2) that binds the ghrelin receptor (GHS-R1a) on pituitary somatotrophs and hypothalamic neurons to trigger pulsatile growth hormone release. The earliest GHRP-class compound characterized in the foundational work of Cyril Bowers in the mid-1980s, it is uniquely defined by pronounced appetite stimulation, which makes it distinctive for cachexia and bulking research but a poor fit for caloric-deficit goals. It also co-stimulates cortisol and prolactin, and has been largely displaced in the community by the cleaner, more selective ipamorelin.
Class
Synthetic hexapeptide GH secretagogue (ghrelin receptor agonist)
Half-life
~15-30 minutes
Routes
Subcutaneous, Intramuscular, Intranasal (research), Intravenous (diagnostic)
Category
Growth Hormone & Performance
Researched benefits
What it's studied for
Pulsatile growth hormone release
Agonism at GHS-R1a on pituitary somatotrophs triggers a sharp, brief GH pulse typically 3-5x pre-injection baseline after 100-300 mcg subcutaneous doses. The mechanism partially antagonizes somatostatin and is synergistic with GHRH signaling.
Pronounced appetite stimulation
By engaging hypothalamic arcuate-nucleus NPY/AgRP neurons, GHRP-6 produces the strongest hunger signal of the common GHRPs, noticeable within 30-60 minutes of injection. This is therapeutically relevant in cachexia, anorexia, and post-illness recovery, and is a feature during caloric-surplus bulking phases.
Muscle recovery and body composition support
Amplified GH and downstream IGF-1 elevation support lean-mass gains and recovery under training load, with detectable body composition effects generally emerging over 8-16 weeks of consistent dosing.
Synergy with GHRH analogs
Combining GHRP-6 (Gq/IP3 pathway) with a GHRH analog such as CJC-1295 or sermorelin (Gs/cAMP pathway) produces a GH pulse 3-5x larger than either mechanism alone, the pharmacologic basis for classical GHRP + GHRH stacks.
Preclinical cardioprotection
In animal cardiac ischemia-reperfusion models GHRP-6 has reduced infarct size and improved ventricular function, effects attributed to CD36 receptor binding independent of GHS-R1a. Clinical translation to human cardiac therapy has not occurred.
Mechanism
How it works
GHRP-6 is a synthetic hexapeptide with the sequence His-D-Trp-Ala-Trp-D-Phe-Lys-NH2 that acts as an agonist at the growth hormone secretagogue receptor type 1a (GHS-R1a) — the same receptor targeted by endogenous ghrelin, GHRP-2, hexarelin, ipamorelin, and oral MK-677. Receptor binding couples to Gq/11, activating phospholipase C to generate IP3 and DAG, releasing intracellular calcium and driving GH granule exocytosis from pituitary somatotrophs within minutes.
Beyond direct somatotroph stimulation, GHRP-6 works through the hypothalamus: it activates arcuate-nucleus circuits, stimulates GHRH neurons to amplify the pituitary response, and partially antagonizes somatostatin, removing the inhibitory gate on GH pulse amplitude. This central action is synergistic with but mechanistically distinct from GHRH, so co-administration with a GHRH analog produces a GH pulse far larger than either agent alone.
The feature that separates GHRP-6 from more selective GHS compounds is its strong engagement of hypothalamic NPY/AgRP appetite neurons. Per unit of GH released, GHRP-6 drives more hunger than GHRP-2 or ipamorelin — an intrinsic consequence of its ghrelin-mimetic receptor pharmacology rather than a dose-titratable side effect. The same non-selective binding profile also produces modest co-stimulation of cortisol/ACTH and prolactin via the HPA axis.
A separate, GHS-R1a-independent mechanism involves binding to the CD36 scavenger receptor, which underlies GHRP-6's observed cardioprotective effects in preclinical ischemia models.
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-6 ships as a white lyophilized powder in 5 mg or 10 mg vials. A standard reconstitution is a 5 mg vial + 2 mL bacteriostatic water, yielding 2.5 mg/mL, so a 100 mcg dose = 0.04 mL = 4 units on a U-100 insulin syringe (150 mcg = 6 units, 200 mcg = 8 units, 300 mcg = 12 units). For smaller injection volumes, 5 mg + 1 mL BAC water gives 5 mg/mL (100 mcg = 2 units). Add water down the vial wall, do not shake — swirl gently 30-60 seconds until the solution is clear and colorless.
Beginner
- Dose
- 100 mcg per injection
- Frequency
- 2x daily (200 mcg/day)
- Timing
- Fasted — pre-breakfast and pre-bed, with a planned meal ready within 30-60 minutes
- Duration
- 12-16 weeks minimum to assess response
- Route
- Subcutaneous
Establish appetite tolerance and meal planning first. Appetite increase is usually clear within the first 2-3 doses; flushing and injection-site redness diminish after week 1.
Intermediate
- Dose
- 100-200 mcg per injection
- Frequency
- 3x daily (300-450 mcg/day)
- Timing
- Fasted — pre-breakfast, pre-training, pre-bed
- Duration
- 12-16 week phases
- Route
- Subcutaneous
Often paired with a GHRH analog in the same syringe for 3-5x GH synergy. Progressive dosing: weeks 1-2 at 100 mcg 2x, weeks 3-4 at 100 mcg 3x, weeks 5-8 at 150 mcg 3x, weeks 9+ at 200 mcg 3x if IGF-1 warrants.
Advanced
- Dose
- 150-200 mcg per injection
- Frequency
- 3x daily (450-600 mcg/day)
- Timing
- Fasted — pre-breakfast, pre-training, pre-bed
- Duration
- 12-16 week bulk phases, then transition to ipamorelin/GHRP-2 for cut or maintenance
- Route
- Subcutaneous
Best deployed in caloric-surplus bulking, post-illness recovery, or cachexia contexts. Doses beyond ~300 mcg per injection show diminishing returns due to GHS-R1a receptor saturation; rigorous macro tracking is required to prevent fat gain.
- Dose fasted, 2-3 hours after the last meal — elevated glucose and insulin blunt GH release.
- Single-injection ceiling is approximately 300 mcg; above this, receptor saturation prevents additional GH release.
- Meal planning is critical: align injections 30-60 minutes before planned eating windows so the strong appetite effect becomes productive rather than sabotaging macro targets. Avoid injecting 90+ minutes before a meal.
- Cycling to preserve GHS-R1a sensitivity: 5 days on / 2 days off weekly, or 8 weeks on / 2 weeks off for a fuller receptor reset.
- Baseline and monitoring labs: IGF-1, fasting insulin, fasting glucose, HbA1c, prolactin, and AM cortisol; recheck at week 8 and week 16, then IGF-1 and glucose every 3 months.
- Store lyophilized vials refrigerated at 2-8°C (stable up to 2 years); use reconstituted solution within 30 days, never freeze, and protect from light.
Evidence
Research & clinical studies (2)
Growth hormone-releasing peptides
Human and animal evidence shows GHRPs including GHRP-6 potently stimulate GH secretion via specific pituitary and hypothalamic receptors, with dose-related effects after IV, subcutaneous, intranasal, and oral administration and synergistic GH release when combined with GHRH.
PMID 9186261Growth hormone-releasing effect of oral growth hormone-releasing peptide 6 (GHRP-6) administration in children with short stature
Oral GHRP-6 at 300 mcg/kg induced a significant GH response in children with short stature comparable to intravenous GHRH-29, with synergistic GH release when combined with oral arginine, demonstrating oral bioavailability and hypothalamic-pituitary secretory activity.
PMID 7581965Combinations
Stacking & blends
GHRP-6 + GHRH Analog (standard synergy stack)
Maximize endogenous GH pulse amplitude
GHRP-6 supplies the ghrelin-pathway signal while a GHRH analog supplies the parallel GHRH-pathway signal; intracellular convergence produces a GH pulse 3-5x either alone. Both are drawn into the same insulin syringe and injected together 2-3x daily fasted.
GH Secretagogue Max
Muscle growth, fat loss, and recovery via maximal GH output
An advanced triple-secretagogue combination: CJC-1295 extends GHRH signaling, ipamorelin provides selective ghrelin-receptor stimulation, and GHRP-6 adds pulse amplitude alongside appetite stimulation for the highest attainable endogenous GH output without exogenous HGH.
Bulk-Phase Performance Stack
Lean mass gains with connective-tissue support during a 12-16 week bulk
GHRP-6 + CJC-1295 drive GH/IGF-1 amplification and appetite for caloric surplus, while BPC-157 and TB-500 support connective and soft tissue under increased training load. Requires disciplined macro planning to avoid excess fat gain.
Safety
Side effects & considerations
Commonly reported effects
Contraindications & cautions
- Active malignancy, especially hormone-responsive cancers
- Strong family history of GH-axis sensitive cancers
- Pregnancy and lactation
- Known hypersensitivity to GHRP-6 or related hexapeptides
- Severe untreated obstructive sleep apnea
- Acute critical illness (sepsis, trauma, respiratory failure)
- Diabetic ketoacidosis or severe uncontrolled diabetes
- Active proliferative retinopathy
- Prolactinoma or significant hyperprolactinemia
- Active eating disorders (binge eating, bulimia)
- Cushing's syndrome or baseline elevated cortisol
The signature effect is dose-related, pronounced appetite stimulation intrinsic to ghrelin-receptor pharmacology, not a titratable side effect. Cortisol and prolactin cross-reactivity are modest and similar to GHRP-2. Chronic use can produce modest insulin resistance and receptor desensitization (mitigated by cycling), and sustained IGF-1 elevation carries theoretical cancer concerns. Use caution with glucocorticoids (reduced GH response), opioids (augmented cortisol/prolactin), and avoid combining with GLP-1 agonists during deficit phases (opposing appetite signals). Discontinue for persistent joint pain, carpal tunnel symptoms, peripheral edema, fasting glucose persistently >110 mg/dL, or worsening sleep apnea.
FAQ
GHRP-6 — common questions
What is GHRP-6?
GHRP-6 (Growth Hormone Releasing Peptide-6) is a first-generation synthetic hexapeptide and ghrelin receptor (GHS-R1a) agonist that stimulates pulsatile pituitary GH release. It is the original GHRP-class compound, predating GHRP-2 and the selective secretagogue ipamorelin, and was developed by Cyril Bowers and Frank Momany at Tulane University in the mid-1980s.
Why does GHRP-6 cause hunger?
GHRP-6 binds the ghrelin receptor in the hypothalamic arcuate nucleus, activating the NPY/AgRP neurons that mediate the appetite-stimulating effects of endogenous ghrelin. This produces the strongest hunger signal of the common GHRPs, typically within 30-60 minutes of injection. It is a function of the receptor binding profile, not a side effect that can be dosed away, which is why more selective peptides like ipamorelin avoid it.
What is the difference between GHRP-6 and GHRP-2?
Both are hexapeptide GHS-R1a agonists with similar GH-release potency and modest cortisol/prolactin elevation, but GHRP-6 produces markedly stronger appetite stimulation for a given GH response, while GHRP-2 delivers slightly higher GH pulse amplitude at equivalent doses with less hunger. Choose GHRP-6 when appetite stimulation is desired (bulking, recovery), GHRP-2 when GH potency is the priority, and ipamorelin for the cleanest pharmacology.
What is the standard GHRP-6 dose?
A common protocol is 100-200 mcg per subcutaneous injection, 2-3 times daily in the fasted state. Beginners start at 100 mcg twice daily and titrate up; intermediate users dose 100-150 mcg three times daily. The single-injection ceiling is about 300 mcg — beyond that, GHS-R1a receptor saturation prevents additional GH release. Meal timing around each injection is essential to make the appetite effect productive.
Can GHRP-6 be stacked with other peptides?
The most meaningful stack is GHRP-6 plus a GHRH analog (sermorelin, CJC-1295 no-DAC, or tesamorelin) in the same injection, which produces a 3-5x amplified GH pulse. It also pairs well with BPC-157 and TB-500 for tissue repair during bulking. Avoid combining it with other GHS-R1a agonists (GHRP-2, ipamorelin, hexarelin, MK-677) because they are mechanistically redundant, and avoid GLP-1 agonists during deficit phases since the appetite signals oppose each other.
Is GHRP-6 good for bulking?
Bulking is arguably GHRP-6's best use case. The appetite stimulation facilitates the higher caloric intake needed for lean-mass gains while GH/IGF-1 amplification enhances anabolic signaling. A classical bulk stack is GHRP-6 150-200 mcg plus CJC-1295 no-DAC three times daily fasted over 12-16 weeks, with a transition to ipamorelin or GHRP-2 for subsequent cut or maintenance phases.
Is GHRP-6 FDA approved or legal?
GHRP-6 is not FDA-approved for any indication. It is sold in the research-peptide market under research-only classification, and some 503B compounding pharmacies include it for physician-supervised off-label use. It is on the WADA Prohibited List (Section S2), so it is banned for competitive athletes and will show up on relevant drug tests.
Does GHRP-6 have any effects beyond GH and appetite?
Yes. In preclinical cardiac ischemia-reperfusion models, GHRP-6 has reduced infarct size and improved ventricular function, effects attributed to binding the CD36 receptor independent of the ghrelin receptor. This has generated interest in GHRP-6 as a cardioprotective research tool, though it has not translated to human cardiac therapy.
