GHRP-6growth hormone-releasing peptide-6 · the original GHRP
The first growth-hormone-releasing peptide ever developed — a synthetic six-amino-acid peptide that triggers a growth-hormone pulse by mimicking ghrelin, the body's hunger hormone. Of all the classic GHRPs, GHRP-6 produces the strongest appetite stimulation. It is not an approved medicine. FDA lists it as a 503B Category 2 bulk substance that may present significant safety risks; it is prohibited in sport under WADA category S2.
First-generation synthetic hexapeptide GH secretagogue and ghrelin/GHSR-1a agonist. It stimulates pituitary somatotrophs to release GH, synergizes with endogenous GHRH, and blocks somatostatin — but it is less GH-selective than later peptides, with notable appetite, prolactin, ACTH and cortisol effects. In a human IV PK study (9 healthy men, 100–400 µg/kg), disposition was biexponential: distribution t½ ≈ 7.6 min, elimination t½ ≈ 2.5 h. FDA flags glucose/insulin-sensitivity, cortisol, and immunogenicity/impurity concerns. No modern therapeutic RCT base exists.
GHRP-6 — His-D-Trp-Ala-Trp-D-Phe-Lys-NH₂ (C₄₆H₅₆N₁₂O₆, MW ≈ 873.0 Da, CAS 87616-84-0, PubChem CID 5486806) — a met-enkephalin–derived hexapeptide with non-natural D-residues. Activates the ghrelin/GHS receptor (GHSR-1a), a Gq/11-coupled GPCR linking GH secretion with appetite, fat accumulation, energy expenditure, and mood. Unusually, its GH-release signaling is PKC/Ca²⁺-dependent and relatively cAMP-independent — mechanistically distinct from GHRH. It also binds the CD36 scavenger receptor, the basis of GHRP-6's preclinical cardioprotection and cytoprotection research.
GHRP-6 is the original growth-hormone-releasing peptide — the molecule that founded the GH-secretagogue class. It reliably stimulates an acute GH pulse and has the strongest appetite signature of the classic GHRPs, but it is unapproved, non-selective (PRL/ACTH/cortisol/glucose effects), and carries FDA-flagged compounding risks. Its most distinctive research frontier is CD36-mediated tissue protection, separate from GH release.
🧪
Primary use case
GH research
Researched as a GH secretagogue that acutely stimulates pituitary GH release; no approved therapeutic indication. Grade B/C.
🔑
Mechanism headline
GHSR-1a
Acts mainly through the ghrelin receptor / GHSR-1a axis, with pituitary and hypothalamic GH-release signaling, plus somatostatin blockade. Grade B/P.
📊
Strongest evidence tier
Human PK/PD
Human studies show acute endocrine effects, oral activity, sleep/hormone effects, and IV pharmacokinetics — but no modern large therapeutic RCT. Grade B.
🍽️
Appetite signature
Strongest GHRP
Ghrelin-receptor biology drives potent hunger stimulation — the most pronounced of the classic GHRPs, a liability or a feature depending on goal. Grade B/P.
💉
Typical research dose
1 µg/kg IV
Human IV endocrine challenge ~1 µg/kg; oral pediatric study used 300 µg/kg. SC community ranges are unapproved (Grade D).
🫀
Distinctive frontier
CD36
Binds the CD36 scavenger receptor, mediating preclinical cardioprotection and cytoprotection independent of GH — the basis of the EP80317 drug lineage. Grade P/C.
⚖️
Key risk · non-selectivity
Glucose · PRL
FDA flags increased blood glucose via reduced insulin sensitivity, cortisol effects, and immunogenicity/impurity risk; PRL/ACTH spillover. Grade D.
⚠️
Regulatory status
503B Cat 2
Not FDA-approved; FDA 503B Category 2 (added Sept 2023); WADA-prohibited at all times. Grade D.
02 · Mechanism of action
How GHRP-6 drives a growth-hormone pulse.
GHRP-6 mimics ghrelin at the GHSR-1a receptor to release GH, synergizes with the body's own GHRH, and blocks the somatostatin brake. Its signaling is unusual — PKC/Ca²⁺-driven rather than cAMP-first — and it engages a second receptor, CD36, that underlies its tissue-protection research. Because the ghrelin receptor governs appetite as well as GH, hunger stimulation is intrinsic, and the peptide is not GH-selective.
Grade B/P
🔑
1 · GHSR-1a / ghrelin receptor agonism
GHRP-6 mimics part of the body's hunger and GH-signaling system, binding the ghrelin receptor (GHSR-1a) to trigger growth-hormone release.
Clinical significance: It activates the ghrelin-receptor pathway in pituitary and hypothalamic GH-regulatory circuits, which is why it raises GH independent of GHRH signaling — and why it simultaneously drives appetite. The ghrelin receptor governs GH secretion, appetite regulation, fat accumulation, energy expenditure, behavior, and mood. The exact tissue-specific signaling bias of GHRP-6 remains incompletely mapped.
Molecular detail: GHSR-1a is a class-A GPCR coupled to Gq/11, originally cloned from pituitary/hypothalamus and later paired with ghrelin as its endogenous ligand. IUPHAR identifies the ghrelin receptor (formerly GHS-R1a) and its role in GH secretion and energy balance. The non-natural D-Trp² and D-Phe⁵ residues, plus the C-terminal amide, confer protease resistance and high receptor affinity.
Grade C/P
📈
2 · Pituitary somatotroph GH release
GHRP-6 makes pituitary somatotroph cells release growth hormone in an acute, dose-dependent pulse.
Clinical significance: Human and animal studies consistently show acute GH increases after GHRP-6 exposure, establishing it as a reliable provocative GH-release agent. The pulse is the foundation for both its research utility and its (unapproved) performance/anti-aging use. The GH response is brief and self-limiting.
Molecular detail: In rat primary pituitary cell culture, GHRP-6 stimulated GH release in a time- and dose-dependent manner, with half-maximal stimulation near 7 × 10⁻⁹ M and maximal near 10⁻⁷ M. The secretory burst reflects direct somatotroph activation layered on disinhibition of endogenous GH-regulatory tone.
Grade C/P
🔗
3 · GHRH synergy & somatostatin blockade
GHRP-6 works best when the body's own GH-releasing hormone (GHRH) is active, and it lifts the somatostatin brake that normally suppresses GH.
Clinical significance: GHRP-6 and GHRH produce synergistic GH release, and GHRP-6 requires endogenous hypothalamic GHRH for maximal stimulation. In rat pituitary cells, combined GHRP-6 + GHRH produced synergistic GH release and potentiated GHRH-related cAMP signaling. This is the mechanistic basis for pairing GHRP-6 with a GHRH analog, and it explains why high somatostatin tone (hyperglycemia, free fatty acids) blunts the response.
Molecular detail: GHRP-6 functionally antagonizes somatostatin (the GH-inhibiting hormone) at hypothalamic and pituitary levels while GHRH drives the Gs–cAMP arm. GHRP-6 requires endogenous hypothalamic GHRH for maximal GH stimulation (Leal-Cerro 1998). The accelerator-plus-brake-release combination accounts for the supra-additive GH pulse when GHRP and GHRH are co-administered.
Grade P/C
⚡
4 · PKC / Ca²⁺ signaling (cAMP-independent)
GHRP-6 uses a different intracellular signaling route than classic GHRH — relying on protein kinase C and calcium rather than cAMP.
Clinical significance: This distinct signaling explains why GHRP-6 and GHRH are synergistic rather than redundant: they converge on the same cell through different second-messenger systems. Pituitary-cell studies describe GHRP-6 GH release as involving PKC and Ca²⁺ but not primarily cAMP-dependent signaling. It also underlies the partial tachyphylaxis seen with repeated dosing.
Molecular detail: GHSR-1a coupling to Gq/11 activates phospholipase C → IP₃/DAG → intracellular Ca²⁺ release and PKC activation, driving GH exocytosis. GHRP-6 alone did not raise intracellular cAMP the way GHRH does, confirming the cAMP-independent pathway. The detailed pathway mapping remains model-dependent.
Grade B/P
🍽️
5 · Appetite / metabolic signaling overlap
Because it acts on the ghrelin system, GHRP-6 strongly affects hunger and metabolic signals — the most potent appetite effect of the classic GHRPs.
Clinical significance: Ghrelin-receptor biology links GH release with appetite, energy expenditure, fat accumulation, and metabolic regulation, so GHRP-6 reliably increases hunger. GHSR-1a is involved in GH secretion, appetite regulation, fat accumulation, energy expenditure, and behavioral/mood signaling. This is a benefit in wasting/cachexia and a liability in obesity, insulin resistance, or diabetes.
Molecular detail: Orexigenic signaling proceeds through GHSR-1a on hypothalamic arcuate-nucleus NPY/AgRP neurons. The clinical magnitude of GHRP-6's appetite effect outpaces GHRP-2 and ipamorelin, consistent with its early reputation as the most "hunger-inducing" GHRP. Direct human therapeutic appetite-modulation data remain limited.
Grade P/C
🫀
6 · CD36 binding & extra-endocrine cytoprotection
Beyond releasing GH, GHRP-6 binds a second receptor — CD36 — that underlies preclinical tissue-protective effects in the heart, brain, and other organs.
Clinical significance: GHRP-class peptides are studied for cardioprotection and cytoprotection that appear independent of GH release. GHRPs bind GHSR-1a and CD36, potentially mediating endocrine and extra-endocrine effects. In a porcine acute-MI model, GHRP-6 reduced myocardial necrosis and infarct size via oxidant-scavenging and pro-survival mechanisms. A parallel anti-fibrotic arm has emerged: topical GHRP-6 prevented hypertrophic scarring in over 90% of treated wounds by downregulating TGF-β1/CTGF. This remains preclinical — not an approved clinical use.
Molecular detail: GHRP-6 binds the CD36 ectodomain (CD36 IC₅₀ ≈ 1.82 µM), activating PI3K/Akt cell-survival signaling, upregulating anti-apoptotic Bcl-2, and downregulating fibrogenic TGF-β1/CTGF. The GHRP-6 scaffold was optimized into selective CD36 azapeptide modulators such as EP80317 for cardiovascular and metabolic disease. This dual-receptor pharmacology distinguishes GHRP-6 from later, GH-selective secretagogues.
L3 · Cascade
Signaling cascade — dual-receptor pharmacology
💉 GHRP-6
IV / oral / SC
→
🔑 GHSR-1a
Gq/11 · PLC · Ca²⁺ · PKC
→
⚙️ GHRH↑ · SST↓
convergent drive
→
📈 GH pulse + appetite
brief burst
→
🔄 IGF-1 · CD36 protection
PRL · ACTH · tissue
L3 · Mechanism summary
Two receptors, two biologies
Driver
Receptor / pathway
Net effect
Evidence
GH secretion
GHSR-1a · Gq/11–PLC–Ca²⁺–PKC
Acute GH pulse
Pituitary-cell
GHRH synergy
Converges with Gs–cAMP arm
Supra-additive GH
Requires endogenous GHRH
Somatostatin blockade
Removes GH brake
Disinhibits pulse
Synergy model
Appetite
Arcuate NPY/AgRP
Strong hunger ↑
Ghrelin biology
Off-target: PRL/ACTH/cortisol
Lactotroph / HPA axis
Spillover
GHRP-class
Cytoprotection
CD36 · PI3K/Akt/Bcl-2
Tissue survival (preclinical)
CD36 binding
L3 · PK summary
Human pharmacokinetics (IV bolus, healthy men)
Parameter
Value
Note
Distribution half-life
7.6 ± 1.9 min
Cabrales 2013 · n=9
Elimination half-life
2.5 ± 1.1 h
Biexponential disposition
IV doses studied
100, 200, 400 µg/kg
PK exposure only — not therapeutic doses
Oral bioavailability
< 1%
Oral activity shown by GH response despite low absolute F
Molecular weight
872.44–873.0 Da
PK paper vs PubChem
L3 · CD36 cytoprotection
The extra-endocrine tissue-protection arm (preclinical)
Effect
Model / finding
Mechanism
Grade
Cardioprotection
Porcine acute-MI: reduced necrosis & infarct size
CD36 · oxidant scavenging
C
Anti-doxorubicin
Prevented myocardial + extra-myocardial damage in rats
Bcl-2 ↑ · mitochondrial protection
C
Anti-fibrotic / wound
Hypertrophic scar prevented >90%
TGF-β1/CTGF ↓ · PI3K/Akt
C
Drug-design lineage
Optimized to EP80317 CD36 azapeptide
CD36 IC₅₀ ≈ 1.82 µM
P
03 · Dosing protocols & models
Route-specific dosing models.
GHRP-6 has no approved therapeutic dosing protocol. The models below separate studied human exposure data (IV, oral, intranasal endocrine challenges) from unvalidated practice-pattern calculator values (subcutaneous). Every non-study figure is a research-page scaffold, not a recommendation. FDA lists GHRP-6 as 503B Category 2 because compounded products may pose immunogenicity risk from aggregation/impurities, with documented concerns around cortisol and blood glucose.
Important · regulatory status
GHRP-6 is not FDA-approved for any indication. FDA lists GHRP-6 as a 503B Category 2 bulk substance that may present significant safety risks (added 29 September 2023), citing immunogenicity/impurity concerns, potential cortisol effects, and increased blood glucose from reduced insulin sensitivity. It is prohibited in sport at all times under WADA category S2 (GH-releasing peptides). All non-study dosing is investigational research-page modeling requiring physician supervision; nothing here is a patient instruction.
PK / PD anchor
The best human PK data come from Cabrales et al. 2013 — nine healthy men given single IV boluses of 100, 200, and 400 µg/kg. Disposition fit a biexponential model with distribution half-life 7.6 ± 1.9 min and elimination half-life 2.5 ± 1.1 h. These are exposure-characterization doses, far above any endocrine-challenge or practice dose, and must not be read as therapeutic targets. Oral activity is established by GH response despite <1% absolute bioavailability.
Intravenous endocrine-challenge model
Human IV endocrine + PK studies · research only
Grade B
Evidence basis
Human IV endocrine studies and a formal IV PK study. Cabrales 2013 Hayashi 1991
Challenge dose
1 µg/kg IV bolus in small normal-male endocrine study context. Marked GH peak
PK-study doses
100 / 200 / 400 µg/kg IV were used to characterize disposition — exposure study, not wellness/therapeutic guidance. Cabrales 2013
Escalation
Not a treatment protocol; escalation should not be implied beyond studied single-dose protocols.
Maintenance / cycle
Not established. Single-dose studies do not define cycling.
IV use carries the highest sterility/compounding risk and must not be presented as consumer self-use. Grade B for studied exposure; D for any protocol extrapolation.
Dose bands · global
Global dose-band reference (working unit µg)
Band
Dose
≈ µg/kg @ 70 kg
Basis
Grade
IV endocrine challenge
~70 µg single
1 µg/kg single
Small human endocrine study
B
Calculator low (SC)
100 µg/admin
1.4
Unvalidated SC practice-pattern
D
Calculator standard (SC)
150–200 µg/admin
2.1–2.9
Unvalidated SC practice-pattern
D
Calculator high (SC)
250–300 µg/admin
3.6–4.3
Unvalidated; triggers caution flags
D/P
Oral endocrine challenge
300 µg/kg single
~21 mg @ 70 kg
Pediatric study; not adult treatment
B/D
IV PK exposure
100–400 µg/kg single
7–28 mg @ 70 kg
PK study only — not protocol guidance
B/D
Titration logic · challenge
Diagnostic / research test decision points
Trigger
Action
Rationale
Pregnancy or possible pregnancy
Do not administer
No adequate safety data
Non-fasting / recent meal
Reschedule
Somatostatin tone and substrate confound GH response
Competitive athlete
Do not administer
WADA-prohibited
Active malignancy
Do not administer
GH/IGF-1 proliferative-axis concern
Biomarker scaffold · challenge
What is measured during a challenge
Marker
Use
Validated for GHRP-6?
Serial GH (ng/mL)
Acute response endpoint
Research context only
IGF-1 (baseline)
Background GH-axis status
Adjunct
Glucose / insulin
FDA-flagged safety signal
No
Cortisol / prolactin
Non-selectivity surveillance
No
Oral endocrine-response model
Pediatric short-stature study · research only
Grade B/D
Evidence basis
A pediatric short-stature study tested oral GHRP-6 300 µg/kg and showed a GH response comparable to IV GHRH challenge; low-dose oral arginine did not enhance it.
Studied dose
300 µg/kg oral single challenge.
Bioavailability
Oral absolute bioavailability is < 1%; oral activity is demonstrated by GH response despite very low systemic exposure.
Escalation / maintenance
No modern therapeutic titration established. Do not translate pediatric endocrine-challenge data into adult treatment instructions.
Monitoring
Growth-axis labs under research/clinical context only; glucose/insulin effects must be flagged.
Pediatric endocrine response ≠ approved pediatric growth therapy. Grade B for acute endocrine response; D for any therapeutic protocol.
Oral context
Why oral GHRP-6 appears in the literature
Point
Detail
Grade
Oral activity
300 µg/kg oral raised GH in children with normal short stature
B
Bioavailability
<1% absolute — large oral doses needed for effect
—
Adult therapeutic dose
Not established
D
Titration logic · oral
Oral-route caution points
Trigger
Action
Rationale
Glucose worsening
Hold
FDA glucose/insulin concern
Pediatric non-research use
Do not use
Not approved growth therapy
Appetite-driven overeating
Reassess
Ghrelin-axis hunger
Intranasal endocrine-response model
Small human study · route evidence, not protocol
Grade B/D
Evidence basis
A small study in 6 healthy men found intranasal GHRP increased plasma GH and IGF-1, while IV 1 µg/kg produced a marked GH peak.
Dose
Not calculator-ready from accessible data; use the study as route-evidence, not protocol evidence.
Reconstitution
Intranasal solutions require spray volume, concentration, and sterility/preservative controls; do not reuse injectable calculator defaults.
Monitoring
Nasal irritation, GH/IGF-1, glucose/insulin sensitivity, cortisol/prolactin if studied.
FDA flags peptide nasal/injectable compounding concerns and GHRP-6 compounding risk. Grade B for route activity; D for protocol.
Route activity · intranasal
Intranasal evidence summary
Finding
Detail
Grade
GH + IGF-1 rise
Intranasal GHRP raised plasma GH and IGF-1 in healthy men
B
Comparator
IV 1 µg/kg gave a markedly larger GH peak in the same study
B
Formulation
No validated sterile intranasal product
D
Subcutaneous practice-pattern model
Community pattern · unvalidated · calculator model only
Grade D/P
Evidence basis
Commonly discussed in peptide practice, but robust controlled human therapeutic protocols are lacking for SC GHRP-6.
Calculator model dose
100 µg per administration as a conservative display band — practice-pattern D, not approved dosing.
Escalation
Inside the educational model only: 100 → 150 → 200 µg if no safety flags. Ladder: 100, 150, 200, 250, 300 µg/admin.
Cycle / washout
Not established. Page may show "4–8 week research cycle / 2–4 week washout" only as unvalidated practice pattern.
Reconstitution
5 mg vial + 2 mL BAC = 2,500 µg/mL; 100 µg = 0.04 mL = 4 U on a U-100 syringe (see calculator).
Monitoring
Fasting glucose, A1c, fasting insulin, IGF-1, edema, BP, sleep/appetite, cortisol/prolactin symptoms — all flagged unvalidated for GHRP-6.
Avoid presenting as clinical treatment. Extra caution in diabetes/insulin resistance, cancer-risk contexts, active edema, pregnancy/lactation, pituitary disease, and competitive athletes. Display cap 300 µg. Grade D/P.
Dose ladder · SC
Conservative SC research ladder (hypothesis only)
Step
Dose
Hold for
Grade
Step 1 (screen)
100 µg SC
Tolerability: flushing, hunger surge, BP
D
Step 2
150 µg SC
Glucose/appetite response
D
Step 3
200 µg SC
Conservative display ceiling
D
Step 4 (cap)
250–300 µg SC
Caution flags; do not exceed without oversight
D/P
Weight-band scaffold · SC
Weight-band interpolation (calculator model only — not a recommendation)
Body weight
Low 1.5 µg/kg
Standard 2.5 µg/kg
High 4.0 µg/kg
55 kg
82.5 µg
137.5 µg
220 µg
65 kg
97.5 µg
162.5 µg
260 µg
75 kg
112.5 µg
187.5 µg
300 µg
85 kg
127.5 µg
212.5 µg
340 µg
95 kg
142.5 µg
237.5 µg
380 µg
105 kg
157.5 µg
262.5 µg
420 µg
Titration logic · SC
Titration decision logic
Trigger
Action
Rationale
Fasting glucose rises / A1c worsens
Hold or de-escalate
FDA flags glucose increase via reduced insulin sensitivity
IGF-1 above age-adjusted range
Hold; evaluate GH-axis exposure
GH/IGF-1 axis stimulation
Edema, paresthesia, carpal-tunnel symptoms
De-escalate or hold
GH/IGF-1 fluid-retention pattern
Headache, visual change, pituitary symptoms
Hard stop / clinical eval
Avoid missing pituitary pathology
Excessive appetite / weight gain
Reassess
Strong ghrelin-axis hunger
Anxiety / high-cortisol symptoms
De-escalate
ACTH/cortisol spillover
Active malignancy / unexplained mass
Hard stop
GH/IGF-1 proliferative concern
Pregnancy / lactation
Hard stop
No adequate safety data
Competitive athlete
Hard stop
WADA-prohibited
Biomarker scaffold · SC
Biomarker monitoring scaffold (none validated for GHRP-6)
Marker
Why monitor
Validated?
IGF-1
Downstream GH-axis exposure
No
Fasting glucose
FDA-flagged glycemic worsening
No — caution
HbA1c
Longer-term glycemic trend
No
Fasting insulin / HOMA-IR
Insulin sensitivity
No
AM cortisol
Cortisol-axis concern
No — FDA context
Prolactin
GHRP-class endocrine spillover
No
Blood pressure / edema
Fluid/cardiometabolic
No
Weight / appetite log
Ghrelin-axis symptom tracking
No
Injection-site exam
Local reaction / sterility
No
GHRH + GHRP combination research model
Mechanistic synergy · not approved dosing
Grade C/D
Evidence basis
Preclinical/pituitary data show GHRP-6 and GHRH/GRF synergize on GH release. Practice pairs GHRP-6 with sermorelin or CJC-1295 (no DAC) — not approved GHRP-6 dosing.
Rationale
GHRP-6 (Gq/PLC/PKC arm) and GHRH (Gs–cAMP arm) converge at the somatotroph for a supra-additive GH pulse; GHRP-6 requires endogenous GHRH for maximal effect.
Escalation
Avoid escalating both agents simultaneously; use separate calculators for each.
Reconstitution
Do not merge concentrations in one vial unless explicitly modeling research-only exposure.
Additive GH/IGF-1 exposure; avoid in active malignancy or unexplained elevated IGF-1. Grade C for synergy mechanism; D/P for protocol.
Synergy model · combo
GHRH-analog + GHRP-6 pairing concept
Component
Receptor / arm
Contribution
Grade
GHRP-6
GHSR-1a · Gq/PLC/PKC
Agonism + somatostatin block
C (synergy)
CJC-1295 / sermorelin
GHRH-R · Gs–cAMP
GHRH-arm amplification
C/D
Net effect
Convergent somatotroph
Supra-additive GH pulse
C/D
Biomarker scaffold · combo
Combination monitoring scaffold (none validated)
Marker
Why monitor
Validated?
IGF-1
Additive downstream exposure
No
Fasting glucose / A1c
Compounded insulin-resistance risk
No
BP / edema
Fluid-retention surveillance
No
Cortisol / prolactin
GHRP-6 non-selectivity
No
L2 · Reconstitution & dose math
Reconstitution & Dose Calculator
For reference only. Not medical dosing advice. The subcutaneous bands modeled here are unvalidated practice patterns, soft-capped at 300 µg. Verify peptide purity, sterility, and storage; only use product from a licensed source.
Concentration
—
Draw volume
—
Units (U-100)
—
Doses per vial
—
Basis
—
04 · Combination protocols
Stacking GHRP-6.
GHRP-6 is unapproved and no controlled combination trials exist. The pairings below reflect mechanistic complementarity and practice patterns, not validated protocols. Because GHRP-6 has the strongest appetite effect of the classic GHRPs and FDA-flagged glucose concerns, any combination magnifies metabolic risk. Combination use of investigational compounds requires physician oversight; GHRP-6 is WADA-prohibited for athletes.
GHRH-Analog Synergy
High Synergy
GHRP-6CJC-1295 (no DAC)Sermorelin
The classic secretagogue pairing. GHRP-6 drives GH via the GHSR-1a Gq/PLC/PKC arm and blocks somatostatin; a GHRH analog drives the Gs–cAMP arm. Preclinical pituitary data show GHRP-6 + GHRH synergize on GH release, and GHRP-6 requires endogenous GHRH for maximal effect. Additive GH/IGF-1 exposure is the core caution. Not an approved protocol.
Component
Arm
Evidence
GHRP-6
GHSR-1a + SST block
C (synergy)
CJC-1295 / sermorelin
GHRH-R
C/D (combo)
Sleep + Recovery Protocol
Moderate Synergy
GHRP-6Sleep hygieneSlow-wave sleep
GHRP-6 has human sleep/hormone study signals, including effects on nocturnal hormone secretion and sleep EEG. It stimulated sleep-related hormone secretion and altered sleep EEG in man. It is not a validated sleep drug, and its appetite, glucose, and cortisol/prolactin effects may conflict with recovery goals. Grade B/D.
Lever
Effect
Grade
Slow-wave sleep
Largest physiologic GH pulse
A (physiology)
GHRP-6 add-on
Sleep/hormone signal
B/D
Appetite / Wasting Support
Moderate Synergy
GHRP-6Nutrition supportCachexia care
GHRP-6's strong ghrelin-receptor appetite stimulation makes it the most plausible GHRP for appetite support in wasting contexts. Ghrelin-receptor biology overlaps appetite and energy balance. The same effect is a liability in obesity, binge-eating, insulin resistance, and diabetes — where it should be avoided. Grade P/D.
Context
Direction
Grade
Cachexia / wasting
Potential benefit
P/D
Obesity / IR / T2DM
Liability
D (avoid)
Tissue / Cardiac Research Model (CD36)
Preclinical
GHRP-6CD36 pathwayEP80317 lineage
A distinctly GHRP-6 frontier: CD36-mediated cytoprotection independent of GH. Synthetic GHRPs bind GHSR-1a and CD36, supporting tissue-protection hypotheses; in animal cardiac models GHRP-6 attenuated ischemic and toxic myocardial damage. Not clinically validated — do not imply cardioprotective treatment. Grade P/C.
Element
Detail
Grade
CD36 binding
IC₅₀ ≈ 1.82 µM; PI3K/Akt/Bcl-2 survival
P
Drug lineage
Optimized to EP80317 azapeptide CD36 modulator
P
GHRP-2 / Ipamorelin Cross-Reference
Comparator
GHRP-6GHRP-2Ipamorelin
Alternatives rather than a stack. GHRP-2 gives higher peak GH with less appetite; ipamorelin is the GH-selective option with minimal PRL/cortisol/appetite. Ipamorelin releases GH without significant ACTH/cortisol/PRL, unlike GHRP-6. Stacking multiple GHSR-1a agonists is redundant and not recommended.
Trait
GHRP-6
GHRP-2
Ipamorelin
Peak GH
High
Highest
Moderate
Appetite
Strongest
Moderate
Minimal
PRL/cortisol
Yes
Moderate
Minimal
Glycemic-Safety Co-Management
Safety Overlay
GHRP-6CGM / glucoseDiet structure
Because GHRP-6 both stimulates appetite and reduces insulin sensitivity, glycemic co-management is the most important overlay — not a peptide partner. FDA specifically flags increased blood glucose via decreased insulin sensitivity. CGM or periodic A1c plus carbohydrate-aware meal timing is the rational pairing. Grade D as a "protocol."
Lever
Purpose
Grade
CGM / A1c
Catch insulin-resistance drift
D
Meal timing
Offset strong appetite effect
D
Hard-Constraint Note
Do Not Combine
Active malignancyUncontrolled diabetesWADA testing
Do not stack GHRP-6 with other GH/IGF-1-promoting agents in people with active malignancy, unexplained mass, uncontrolled diabetes/insulin resistance, untreated sleep apnea, severe edema, or competitive-sport exposure. GHRP-6 is prohibited at all times in sport. These are absolute stop conditions regardless of partner agent.
Condition
Status
Active malignancy / pregnancy
Absolute avoid
Uncontrolled diabetes
Avoid
WADA-tested athlete
Prohibited
Clinical note — GHRP-6's most defensible combination rationale is mechanistic synergy with GHRH analogs, but that is precisely where additive GH/IGF-1 exposure and GHRP-6's glucose/appetite effects compound. No combination has regulatory validation. The safest "stack" is a glycemic and IGF-1 monitoring overlay layered onto physician-supervised, time-limited use — and avoidance entirely in the metabolic and oncologic risk groups above.
05 · Safety & contraindications
Safety profile & contraindications.
GHRP-6's safety signal is dominated by FDA-flagged metabolic concerns (blood glucose via reduced insulin sensitivity, cortisol effects, immunogenicity/impurity risk), its strong appetite stimulation, non-selective PRL/ACTH/cortisol spillover, and the general GH-axis adverse pattern (edema, carpal-tunnel symptoms). Long-term safety is unstudied.
Observed / regulatory safety concerns
Increased blood glucose / reduced insulin sensitivityFDA explicitly lists potential blood-glucose increase due to decreased insulin sensitivity. The headline metabolic concern. Grade D.
Cortisol-axis effectFDA flags a potential cortisol effect; anxiety/insomnia/high-cortisol symptoms warrant de-escalation. Grade D.
ACTH / cortisol / prolactin spilloverGHRP-class human endocrine studies show PRL/ACTH/cortisol activity (hexarelin comparison); GHRP-6 shares this class risk. Grade B/D.
Immunogenicity / aggregation / impuritiesFDA flags peptide-related impurity and aggregation concerns for compounded GHRP-6. Grade D.
GH / IGF-1 overexposureMechanism-driven; monitor IGF-1 in any research context. GH-axis stimulation. Grade D.
Appetite increaseStrongest of the classic GHRPs; mechanism-derived through ghrelin-receptor biology. Ghrelin axis. Grade P/D.
Injection-site / sterility issuesRoute/product-quality risk for non-approved injectables. Grade D.
Sleep-apnea worseningGH-axis fluid/soft-tissue effects may aggravate airway symptoms (theoretical).
Monitoring scaffold
Baseline
IGF-1, fasting glucose, HbA1c, fasting insulin (HOMA-IR), lipid panel, BP, weight/appetite log. AM cortisol and prolactin if baseline risk or symptoms. Pregnancy test if reproductive potential. Pituitary imaging if a mass is suspected. Document WADA status for athletes.
During use
Fasting glucose every 2–4 weeks, A1c at 8–12 weeks, IGF-1 at 4–8 weeks; BP/edema and appetite/weight weekly; cortisol/prolactin if symptomatic; injection-site exam each administration. Hold for IGF-1 above age-adjusted range. None of these thresholds is validated specifically for GHRP-6.
Stop / escalate triggers
Hard-stop on pregnancy, active malignancy/unexplained mass, pituitary symptoms (headache/visual change), or WADA-tested status. De-escalate on rising glucose/A1c, new edema/carpal-tunnel, excessive appetite/weight gain, or cortisol/prolactin symptoms. No response without adverse signals is not a reason to escalate an unvalidated protocol.
Contraindications & cautions
Condition
Concern
Severity · grade
Active cancer / unexplained mass
GH/IGF-1 axis exposure may be undesirable
High
Uncontrolled diabetes
FDA flags glucose/insulin-sensitivity concern
High
Severe insulin resistance / metabolic syndrome
Potential worsening glycemic control
High
Pregnancy / lactation
No adequate safety data
High
Pediatric use outside formal research
Oral pediatric study ≠ approved growth therapy
High
Competitive athlete
WADA-prohibited
High
Pituitary tumor / acromegaly history
GH-axis stimulation
High
Untreated sleep apnea
GH-axis / fluid-retention theoretical concern
Moderate–High
Significant edema / heart failure
Fluid-retention / metabolic concern
Moderate–High
Known peptide hypersensitivity
Immunogenicity concern
Moderate–High
Obesity / binge-eating
Strong appetite stimulation liability
Caution
Non-sterile / unverified product
Compounding / endotoxin / aggregation risk
Avoid
Concurrent corticosteroids
Compounded HPA-axis effects
Monitor
Proliferative diabetic retinopathy
Growth-factor concern
High
Carpal-tunnel / neuropathy history
GH/IGF-1 fluid-tissue effects
Monitor
Thyroid disorder (untreated)
GH-axis interacts with thyroid economy
Monitor
Polypharmacy with HPA-active agents
Compounded ACTH/cortisol effects
Monitor
Binge-eating / disordered eating
Strong ghrelin-axis appetite stimulation
Avoid
Severe renal / hepatic impairment
Altered clearance; limited data
Caution
Adolescents with open growth plates (non-research)
Growth-axis manipulation outside diagnosis
Avoid
06 · Trials & evidence base
What the evidence actually shows.
GHRP-6 has moderate evidence for acute GH-secretagogue activity and human PK/endocrine-response data, but low evidence for therapeutic protocols, long-term outcomes, safety monitoring, or disease-specific benefit. The base is strongest for "GHRP-6 acutely stimulates GH release" and weakest for any clinical anti-aging, performance, recovery, or tissue-repair use.
Discovery · 1980s
Bowers
The first highly potent GHRP. By 1984 GHRP-6 helped show GHRP action was distinguishable from GHRH, founding the GH-secretagogue class. Bowers / GHRP series second-generation hexapeptide overview.
Human PK · 2013
n=9
Cabrales: single IV boluses 100/200/400 µg/kg; biexponential PK; distribution t½ 7.6 min, elimination t½ 2.5 h. The firmest PK anchor.
Human oral · 1995
n=13
Bellone: oral 300 µg/kg increased GH in children with normal short stature; arginine did not enhance the effect. Oral activity.
Preclinical cardio · 2006+
CD36
Porcine acute-MI: GHRP-6 reduced myocardial necrosis ~78% and infarct thickness ~50% via oxidant scavenging. Cardioprotection.
BHuman PK · intravenous
Cabrales et al. 2013 — IV pharmacokinetics in 9 healthy men
Single IV boluses of 100, 200, and 400 µg/kg; disposition fit a biexponential model with distribution half-life 7.6 ± 1.9 min and elimination half-life 2.5 ± 1.1 h. The definitive human PK characterization of GHRP-6.
Bellone et al. 1995 — oral GHRP-6 in children with short stature
Oral GHRP-6 at 300 µg/kg increased GH secretion in 13 children with normal short stature, with a response comparable to IV GHRH challenge; coadministered low-dose oral arginine did not enhance the effect.
Hayashi et al. 1991 — intranasal GHRP-6 raises GH and IGF-1
In 6 normal men, intranasal administration of His-D-Trp-Ala-Trp-D-Phe-Lys-NH₂ increased plasma GH and IGF-1, while an IV 1 µg/kg bolus produced a marked GH peak — establishing multi-route activity.
Frieboes et al. 1995 — sleep-related hormone secretion & EEG
Repetitive IV GHRP-6 stimulated sleep-related hormone secretion and altered sleep EEG architecture in man — the basis for the "sleep/recovery" framing, though not a validated sleep therapy.
Endocrine-challenge study of the GHRP/hexarelin class documented age-related variation in GH and in ACTH/cortisol responses — the canonical demonstration of GHRP-class non-selectivity relevant to GHRP-6's risk profile.
de Sá / Peña-Bello et al. 2010 — GHRP-6 in type 1 diabetes
ΔAUC GH after ghrelin, GHRP-6, and GHRH did not differ significantly between type 1 diabetes and controls, informing how the GH-axis response behaves in a metabolic-disease population.
Leal-Cerro et al. 1998 — GHRP-6 requires endogenous GHRH
Demonstrated that GHRP-6 requires endogenous hypothalamic GHRH for maximal GH stimulation — the mechanistic foundation for GHRP+GHRH synergy and for the blunted response when GHRH tone is low.
Cheng et al. 1989 — GHRP-6 + GHRH synergy in pituitary cells
In rat primary pituitary cell culture, GHRP-6 stimulated GH release dose- and time-dependently and synergized with GRF/GHRH while potentiating GHRH-related cAMP signaling — GHRP-6 alone did not raise cAMP comparably.
Lei et al. 1995 — PKC/Ca²⁺, cAMP-independent GH release
Pituitary-cell mechanistic work establishing that GHRP-6 stimulates GH secretion through PKC and Ca²⁺ signaling rather than primarily cAMP — the second-messenger basis for its synergy with GHRH.
Authoritative receptor annotation describing the ghrelin receptor's role in GH secretion and energy-balance biology — the receptor through which GHRP-6 exerts its endocrine and appetite effects. The endogenous ligand ghrelin was identified only later, after the synthetic GHRPs.
Berlanga-Acosta et al. 2017 — GHRPs, GHS-R1a & CD36 cytoprotection
Historical appraisal documenting that GHRPs bind both GHS-R1a and CD36, mediating endocrine and extra-endocrine (cardioprotective/cytoprotective) effects via PI3K/Akt survival signaling — the conceptual core of GHRP-6's tissue-protection research.
GHRP-6 cardioprotection — porcine MI & coronary-ligation models
In animal cardiac models including permanent coronary ligation and acute MI, GHRP-6 attenuated myocardial necrosis and infarct size through oxidant-scavenging and CD36/GHSR-1a pro-survival mechanisms — preclinical, not an approved use.
The GHRP-6 scaffold (CD36 IC₅₀ ≈ 1.82 µM) was optimized into selective azapeptide CD36 modulators such as EP80317, showing cardioprotective and anti-atherosclerotic effects — a translational lineage distinct from GH release.
Fernández-Mayola et al. 2018 — GHRP-6 prevents hypertrophic scarring
In a rabbit hypertrophic-scar model, topical GHRP-6 prevented keloid onset in over 90% of treated wounds and downregulated pro-fibrotic TGF-β1/CTGF while inducing PPARG and MMP-13 — early proteome evidence for a CD36-linked anti-fibrotic action.
Topical GHRP-6 increased wound-closure rate and reduced inflammatory infiltrate in rats; CD36 — a GHRP-6 receptor — was abundantly represented in cutaneous granulation tissue, supporting a CD36-agonist healing mechanism.
Sosa-Hernández et al. 2024 — GHRP-6 vs doxorubicin cardiotoxicity
GHRP-6 prevented doxorubicin-induced myocardial and extra-myocardial damage in rats by attenuating pro-oxidant activity, protecting mitochondrial ultrastructure, and upregulating anti-apoptotic Bcl-2 — cytoprotection extending to liver, kidney, and intestine.
GRADE summary — GHRP-6 earns Grade B for acute GH-secretagogue activity (consistent human PK/endocrine data across IV, oral, and intranasal routes) and Grade C/P for its CD36-mediated cytoprotection, anti-fibrotic, and cardioprotection research. It is Grade D for therapeutic protocols, long-term outcomes, validated monitoring thresholds, and disease-specific benefit. What is missing: large modern RCTs, standardized SC dosing trials, long-term safety, validated biomarker thresholds, and route-specific bioavailability data. Honest positioning: "the original GH secretagogue with solid acute-response evidence and a distinctive CD36 tissue-protection frontier — but no validated therapeutic use, strong appetite/glucose liabilities, and FDA-flagged compounding risk."
07 · Compare & contrast
GHRP-6 vs the secretagogue field.
GHRP-6 is the first-generation anchor of the class: reliable GH release, the strongest appetite effect, notable non-selectivity, and a unique CD36 tissue-protection profile. GHRP-2 gives higher peak GH with less hunger; ipamorelin is the GH-selective choice; MK-677 is the oral, long-acting non-peptide option.
Agent
Mechanism class
Primary position
Routes
Human evidence
Status
GHRP-6
GHSR-1a + CD36 agonist; GHRP
Original GHRP; strongest appetite; CD36 tissue research
IV · oral · intranasal · SC practice
Human acute endocrine + PK; limited therapeutic trials
Not FDA-approved; FDA 503B Cat 2; WADA-banned
GHRP-2 / pralmorelin
GHSR-1a agonist
Higher peak GH; Japan diagnostic approval
IV · nasal · oral · SC
Human PD + Japan diagnostic
Japan diagnostic; not FDA; WADA-banned
Ipamorelin
GHSR-1a agonist (selective)
GH-selective; minimal PRL/cortisol/appetite
SC research
Human/animal PD
Not FDA; FDA 503B Cat 2; WADA-banned
Hexarelin / examorelin
GHSR-1a agonist (potent)
Potent; strong adrenal-axis spillover; cardiac research
IV/SC research
Human endocrine data
Not FDA; WADA-banned
MK-677 / ibutamoren
Oral non-peptide GHSR-1a agonist
Oral, long-acting; sustained IGF-1; more fluid retention
L1 · Consumer — GHRP-6 is a synthetic peptide studied for its ability to trigger the body's growth-hormone release system. It is not an approved medication, and its effects on appetite, blood sugar, cortisol, and hormone balance make it a high-caution research peptide. Of the classic GHRPs, it causes the most hunger.
L2 · Clinical — GHRP-6 is a first-generation growth-hormone-releasing peptide that activates the ghrelin/GHS-R1a pathway and acutely stimulates GH release in humans. The clinical evidence base supports endocrine response and pharmacokinetic characterization, but not validated therapeutic protocols, long-term safety, or routine clinical use. FDA flags glucose, cortisol, and immunogenicity concerns.
L3 · Research — GHRP-6, His-D-Trp-Ala-Trp-D-Phe-Lys-NH₂, is a synthetic hexapeptide GH secretagogue engaging GHS-R1a/ghrelin-receptor biology and stimulating somatotroph GH release through PKC/Ca²⁺ signaling that is mechanistically distinct from classic GHRH/cAMP signaling. Its profile spans pituitary GH secretion, GHRH synergy, somatostatin blockade, strong ghrelin-axis appetite overlap, and CD36-mediated extra-endocrine tissue-protection — the lattermost a genuine drug-design frontier (EP80317).
08 · References & evidence
Source register.
Evidence grades reflect the strength of support for the specific claim cited, not the prestige of the journal. GHRP-6's human PK and multi-route endocrine-response studies are its firmest evidence; mechanistic, CD36, and cardioprotection sources support specific mechanism and tissue-protection claims.