IGF-1 LR3 is a modified version of insulin-like growth factor 1 (IGF-1) with an extended N-terminal sequence (13 additional amino acids) and an arginine-to-glutamic acid substitution at position 3. These modifications dramatically reduce binding to IGF-binding proteins (IGFBPs), resulting in a half-life of 20-30 hours (vs 12-15 hours for native IGF-1) and approximately 3x greater potency. It is one of the most potent anabolic peptides available and is WADA-banned.
Category: Growth Factor. Evidence rating: D (animal/preclinical only).
Clinical status: No clinical trials for therapeutic use. Research compound only.
IGF-1 LR3 binds to IGF-1 receptors on target cells with high affinity, initiating tyrosine kinase signaling that activates the PI3K/Akt/mTOR pathway, increasing protein synthesis, glucose uptake, and cellular survival while inhibiting muscle protein breakdown (anti-catabolic). Its low affinity for…
Research base: 0 registered clinical trials and 3 indexed publications reference IGF-1 LR3.
Safety considerations: Hypoglycemia risk — IGF-1 has insulin-like glucose-lowering effects; Potential organ enlargement with chronic use (intestinal growth observed in animals); Joint pain, water retention, carpal tunnel-like symptoms (GH/IGF axis effects).
Reviewed by the PeptideAtlas Editorial Team. Last reviewed: 2026-07-06.
Related peptides: Follistatin 344, MGF, IGF-1 DES.
Compare: IGF-1 LR3 vs Follistatin 344, IGF-1 LR3 vs MGF, IGF-1 LR3 vs IGF-1 DES.
IGF-1 LR3 has 13 extra N-terminal amino acids and an Arg→Glu substitution at position 3. This reduces binding to IGF-binding proteins by ~100x, resulting in a longer half-life (20-30 hours vs 12-15 hours) and approximately 3x greater potency. More of the peptide reaches target tissues in active form.
There are no formal human safety studies. Known risks include hypoglycemia, organ growth (especially intestinal), and theoretical cancer promotion via IGF-1R signaling. It is one of the higher-risk peptides due to its potent growth factor activity.
IGF-1 LR3 is a modified version of Insulin-like Growth Factor 1 with an extended half-life, researched for muscle growth and cellular proliferation.
IGF-1 LR3 has been studied for: Muscle growth research, Cellular proliferation, Recovery. Long-acting IGF variant; significant muscle research interest.
Long-acting IGF-1 variant that promotes cellular growth, muscle hypertrophy, and may have enhanced tissue-specific effects.