IGF-1 LR3 vs Sermorelin
A neutral, side-by-side comparison of two performance & growth hormone peptides — their mechanisms, dosing ranges, administration routes, side effects, and research evidence. For research and educational purposes only.
IGF-1 LR3
IGF-1 LR3 (Long Arg3 IGF-1) is a synthetic analogue of Insulin-like Growth Factor 1 with an amino acid substitution at position 3 and a 13-amino acid N-terminal extension. These modifications prevent binding to IGF-binding proteins (IGFBPs), dramatically extending its half-life from ~12 minutes (native IGF-1) to approximately 20–30 hours. IGF-1 LR3 is widely used in research for its ability to promote cellular growth, protein synthesis, hyperplasia, and nutrient uptake into muscle tissue.
Full profileSermorelin
Sermorelin is a synthetic analog of the first 29 amino acids of GHRH (Growth Hormone-Releasing Hormone). It was FDA-approved for pediatric GH deficiency diagnosis and is widely used off-label in anti-aging and performance medicine. It stimulates pulsatile GH release more physiologically than exogenous GH.
Full profile| IGF-1 LR3 | Sermorelin | |
|---|---|---|
| Category | Performance & Growth Hormone | Performance & Growth Hormone |
| Also known as | Insulin-like Growth Factor-1 Long R3, Long R3 IGF-1, Increlex (human equivalent) | GHRH 1-29, GRF 1-29 NH2, Geref |
| Evidence | Research-stage | FDA-approved |
| Dosing range | 20mcg–100mcg mcg, Once daily post-workout, on training days only (common protocol) | 100mcg–500mcg mcg, once daily (before sleep) |
| Administration | Subcutaneous injection, Intramuscular injection (into the trained muscle — site-specific protocols) | Subcutaneous injection |
| Key side effects | Hypoglycemia (clinically significant — monitor blood sugar carefully), Jaw and organ growth with chronic high-dose use (theoretical at research doses), Fatigue and headaches, Joint pain | Injection site redness, Headache, Flushing, Dizziness |
| Cited sources | 3 references | 1 reference |
Key differences
- Evidence level differs: IGF-1 LR3 is research-stage, while Sermorelin is fda-approved.
- Administration: IGF-1 LR3 — Subcutaneous injection, Intramuscular injection (into the trained muscle — site-specific protocols); Sermorelin — Subcutaneous injection.
- Frequency: IGF-1 LR3 is typically Once daily post-workout, on training days only (common protocol); Sermorelin is once daily (before sleep).
- Research depth: this profile cites 3 sources for IGF-1 LR3 vs 1 for Sermorelin.
How each works
IGF-1 LR3
In vitro and animal research establishes IGF-1 LR3 as a potent anabolic and growth-promoting agent. It activates the IGF-1 receptor (IGF-1R) and downstream PI3K/Akt and MAPK/Erk pathways, promoting skeletal muscle hypertrophy and satellite cell activation. Its extended half-life makes it far more active systemically than native IGF-1. Research also documents its role in connective tissue repair, nerve regeneration, and fat oxidation. Human research is limited — most data comes from cancer cell biology and athletic performance settings.
Sermorelin
Sermorelin works by binding pituitary GHRH receptors to stimulate GH secretion within the body's natural feedback loop. Unlike synthetic GH, it does not suppress endogenous production. Clinical studies show improved body composition, sleep quality, and IGF-1 levels in GH-deficient adults. Its short half-life (~10 min) means it requires daily dosing.
This comparison aggregates public research and structured profile data for informational purposes only. It is not medical advice and does not recommend either compound for human use. Consult a qualified healthcare provider before considering any peptide.