Side-by-side · Research reference
GHRP-2vsIGF-1 LR3
Side-by-side comparison across mechanism, dosage, evidence, side effects, administration, and stack synergies. Citations on every claim where available.
APhase 2HUMAN-REVIEWED15/42 cited
BAnimal-StrongHUMAN-REVIEWED10/58 cited
GHRP-2
Hexapeptide GHRP · Phase 2 (clinical diagnostic)
SQ · Multiple sites · 1–3×/day
IGF-1 LR3
IGF-1 Analogue · Research
3–10×Potency vs IGF-I
Low IGFBPBinding affinity
ResearchStatus
Research only · SQ typical in animal models
01Mechanism of Action
Parameter
GHRP-2
IGF-1 LR3
Primary target
Ghrelin receptor (GHS-R1a) on anterior pituitaryBowers 1990
IGF-1 receptor (IGF-1R)McTavish 2009
Pathway
GHS-R1a → Gαq → Ca²⁺ → GH vesicle exocytosisBowers 2002
IGF-1R → IRS-1 → PI3K/Akt → Cell proliferation, protein synthesis, anti-apoptosisMuhlbradt 2009
Downstream effect
Strong GH pulse + IGF-1 elevation; appetite increase via ghrelin agonismBowers 2002
Enhanced cell proliferation, muscle anabolism, inhibition of apoptosis, increased telomerase activity
Feedback intact?
Yes, with somatostatin feedback active
No — exogenous IGF analogue bypasses GH-mediated regulation
Origin
Synthetic hexapeptide; developed by Bowers/Tulane group in the 1980sBowers 1990
Synthetic 83-AA analogue: 13-AA N-terminal extension + Arg substitution at position 3
Antibody development
—
—
02Dosage Protocols
Parameter
GHRP-2
IGF-1 LR3
Frequency
1–3× per day
—
Lower / starter dose
50 mcg per dose
—
Duration
8–12 weeks on / 4 off (anecdotal)
—
Reconstitution
Bacteriostatic water
—
Timing
Pre-sleep + fasted preferred
—
Research dose (animal models)
—
Variable by protocol and species
In vivo murine atherosclerosis studies used sustained delivery.
In vitro typical concentration
—
10–1000 ng/mLThomas 2007
Dose-dependent effects on follicle growth and estradiol production.
Half-maximal stimulation
—
0.6 nM LR3 vs 1.5 nM native IGF-1Price 2004
2.5-fold greater potency in lung fibroblast proliferation.
Human use
—
Not FDA-approved; no published human trials
03Metabolic / Fat Loss Evidence
Parameter
GHRP-2
IGF-1 LR3
Mechanism
—
IGF-1R activation → lipolytic signaling; secondary to anabolic effects
Direct lipolytic evidence
—
Minimal — primarily anabolic/anti-apoptotic in literature
Atherosclerotic plaque effects
—
Reduced stenosis and core size in ApoE-KO micevon 2011
Plaque stabilization via vSMC phenotype modulation, not direct fat loss.
Human data
—
None published
04Side Effects & Safety
Parameter
GHRP-2
IGF-1 LR3
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
—
Hypoglycemia risk
—
Theoretical — IGF-1 analogues can lower blood glucose
Excessive cell proliferation
—
Mitogenic signaling; theoretical tumor promotion risk
Telomerase activation
—
2–10-fold increase in prostate cancer cells (PC-3, DU-145, LAPC-4)Wetterau 2003
Critically involved in cancer cell immortalization.
Oocyte degeneration
—
Increased oocyte degeneration at high doses (≥1000 ng/mL) in bovine folliclesThomas 2007
Unregulated anabolism
—
Bypasses physiological GH/IGF-1 feedback; no pulsatility control
Unknown human safety profile
—
No published human trials; safety data absent
Absolute Contraindications
GHRP-2
- ·Active malignancy
- ·Pregnancy / breastfeeding
IGF-1 LR3
- ·Active malignancy or history of cancer
- ·Not approved for human use
Relative Contraindications
GHRP-2
- ·Untreated diabetes
IGF-1 LR3
- ·Diabetes or glucose intolerance
- ·Family history of cancer
05Administration Protocol
Parameter
GHRP-2
IGF-1 LR3
1. Reconstitution
Add 2 mL bacteriostatic water to 5 mg vial → 2.5 mg/mL.
IGF-1 LR3 is not FDA-approved for human use. All administration data derives from animal or in vitro studies.
2. Injection site
SQ — abdomen or thigh. Rotate sites.
Subcutaneous or intraperitoneal injection in animal models. In vitro: added directly to culture medium at concentrations of 10–1000 ng/mL.Thomas 2007
3. Timing
Pre-sleep + fasted preferred.
Lyophilised powder reconstituted in sterile water or buffered saline per manufacturer protocol. Store at 2–8 °C after reconstitution.
4. Storage
Lyophilised: room temp, light-protected. Reconstituted: refrigerate ≤30 days.
Enhanced stability vs native IGF-1 due to reduced IGFBP binding; exact half-life in vivo not fully characterized in humans.
5. Needle
29–31G, 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
IGF-1 LR3
+ GHRP-6
Multi-pathwayGHRP-6 stimulates endogenous GH release, which drives hepatic IGF-1 synthesis. IGF-1 LR3 provides exogenous, IGFBP-resistant IGF signaling. Combining upstream GH stimulation with downstream IGF receptor activation creates a dual-pathway anabolic effect. However, this bypasses natural feedback and carries compounded mitogenic risk.
- GHRP-6
- 100–200 mcg SQ · 2–3× daily
- IGF-1 LR3
- Research doses variable · post-workout typical in animal models
- Note
- Research context only — no human protocols exist
- Primary benefit
- Theoretical maximal anabolic signaling (GH + IGF axes)
+ Ipamorelin
Multi-pathwayIpamorelin (selective GHRP) stimulates pulsatile GH release without cortisol/prolactin elevation. IGF-1 LR3 directly activates IGF-1R independent of GH. This stack targets both upstream (GH secretion) and downstream (IGF receptor) nodes but eliminates physiological feedback, raising safety concerns around unchecked proliferation.
- Ipamorelin
- 200–300 mcg SQ · evening
- IGF-1 LR3
- Research doses only · timing variable
- Caution
- No human data; animal/in vitro only
- Primary benefit
- Dual-axis anabolic signaling (theoretical)