Side-by-side · Research reference
GHRP-2vsRetatrutide
Side-by-side comparison across mechanism, dosage, evidence, side effects, administration, and stack synergies. Citations on every claim where available.
APhase 2Reviewed15/42 cited
BPhase 2Reviewed10/41 cited
GHRP-2
Hexapeptide GHRP · Phase 2 (clinical diagnostic)
SQ · Multiple sites · 1–3×/day
Retatrutide
Triple-receptor agonist · Phase 3
SQ · Abdomen · Once weekly
01Mechanism of Action
Parameter
GHRP-2
Retatrutide
Primary target
Ghrelin receptor (GHS-R1a) on anterior pituitaryBowers 1990
GLP-1R + GIPR + Glucagon receptor (triple agonism)Jastreboff 2023
Pathway
GHS-R1a → Gαq → Ca²⁺ → GH vesicle exocytosisBowers 2002
Triple-receptor activation → ↑insulin (GLP-1+GIP), ↓gastric emptying, ↑lipid handling, ↑energy expenditure (glucagon component)Jastreboff 2023
Downstream effect
Strong GH pulse + IGF-1 elevation; appetite increase via ghrelin agonismBowers 2002
Maximal weight loss across class. Glucagon component drives lipolysis and energy expenditure beyond GLP-1+GIP aloneJastreboff 2023
Feedback intact?
Yes, with somatostatin feedback active
—
Origin
Synthetic hexapeptide; developed by Bowers/Tulane group in the 1980sBowers 1990
Synthetic peptide engineered for balanced affinity at three incretin / glucagon receptorsJastreboff 2023
Antibody development
—
—
02Dosage Protocols
Parameter
GHRP-2
Retatrutide
Standard dose
100–300 mcg per injectionBowers 1990
12 mg / week (max efficacy)Jastreboff 2023
Phase 2 trial dose. Phase 3 dosing TBD.
Frequency
1–3× per day
Once weekly
Lower / starter dose
50 mcg per dose
—
Evidence basis
Phase 2 + clinical diagnostic useBowers 1990
Phase 2 trial; Phase 3 ongoingJastreboff 2023
Duration
8–12 weeks on / 4 off (anecdotal)
Indefinite for chronic indication (presumed)
Reconstitution
Bacteriostatic water
Investigational; not commercially available
Timing
Pre-sleep + fasted preferred
Any time of day
Titration schedule
—
2 mg → 4 mg → 8 mg → 12 mg over 16 weeks
04Side Effects & Safety
Parameter
GHRP-2
Retatrutide
Prolactin elevation
Mild but measurable
—
Hunger
Strong appetite increase
—
Injection site reaction
Mild erythema
—
IGF-1 elevation
Strong; monitor with chronic high-dose use
—
Cancer risk
Contraindicated in active malignancy
—
Pregnancy / OB
Avoid
Avoid (insufficient data)
Glucose handling
—
Glycemic improvement; rare hyperglycemia from glucagon component
Pancreatitis risk
—
Class warning
Thyroid C-cell tumours
—
Class warning (presumed)
Absolute Contraindications
GHRP-2
- ·Active malignancy
- ·Pregnancy / breastfeeding
Retatrutide
- ·MTC personal or family history (presumed class effect)
- ·Pregnancy / breastfeeding
Relative Contraindications
GHRP-2
- ·Untreated diabetes
Retatrutide
- ·Severe gastroparesis
- ·History of pancreatitis
- ·Severe cardiovascular disease (HR signal)
05Administration Protocol
Parameter
GHRP-2
Retatrutide
1. Reconstitution
Add 2 mL bacteriostatic water to 5 mg vial → 2.5 mg/mL.
Investigational peptide. Research vials reconstituted with bacteriostatic water per label.
2. Injection site
SQ — abdomen or thigh. Rotate sites.
SQ — abdomen, thigh, or upper arm. Rotate weekly.
3. Timing
Pre-sleep + fasted preferred.
Once weekly, same day.
4. Storage
Lyophilised: room temp, light-protected. Reconstituted: refrigerate ≤30 days.
Refrigerate 2–8 °C. Light-protected.
5. Needle
29–31G, 4–8 mm insulin syringe.
27–31G, 4–8 mm insulin syringe.
06Stack Synergy
GHRP-2
+ CJC-1295 (no DAC)
StrongGHRP-2 + CJC-1295-no-DAC is a higher-amplitude alternative to the ipamorelin + CJC-1295 stack. GHRP-2 produces a stronger pulse but with cortisol + prolactin signal — choose when maximum GH amplitude is the goal and the side-effect tolerance is acceptable.
- GHRP-2
- 100–200 mcg SQ · pre-sleep
- CJC-1295 (no DAC)
- 100 mcg SQ · same injection
- Primary benefit
- High-amplitude GH pulse, body composition
Retatrutide
— no documented stacks