IGF-1 LR3 is a synthetic analog of insulin-like growth factor-1 (IGF-1), modified by arginine substitution at position 3 and addition of a 13-amino-acid N-terminal extension. This modification fundamentally changes pharmacokinetics: native IGF-1 rapidly binds insulin-like growth factor binding proteins (IGFBP 1–6), which hold it in inactive form in the bloodstream. The Arg-3 substitution reduces IGFBP affinity approximately 1,000-fold, giving the molecule an active half-life of 20–30 hours versus 6–10 hours for native IGF-1 and substantially higher tissue receptor bioavailability.
Binding to IGF-1R on muscle cell surfaces, the peptide simultaneously activates two signaling pathways: PI3K-Akt-mTOR, initiating protein synthesis and suppressing muscle fiber proteolysis, and MAPK/ERK, stimulating proliferation and differentiation of satellite cells — muscle stem cells responsible for increasing myofibril number. This creates a dual anabolic effect: hypertrophy of existing fibers through enhanced protein synthesis and hyperplasia through satellite cell activation — a mechanism unattainable with conventional GH/IGF-1 endogenous axis stimulation. In parallel, glucose and amino acid uptake by cells is enhanced, and tissue-level insulin sensitivity improves.
Beyond muscle, IGF-1 LR3 exerts systemic trophic action: neuroprotection via IGF-1R activation in neurons, support of connective tissue repair and collagen synthesis. The key risk is linked precisely to the breadth of the molecule's action: IGF-1 receptors are also expressed on transformed cells, so use in oncological disease or predisposition requires careful assessment. Hypoglycemia monitoring is equally important — structural similarity to insulin makes this clinically significant.
💪 Muscle anabolism (hypertrophy + hyperplasia): ★★★★★
🔧 Recovery and tissue repair: ★★★★☆
🍬 Insulin sensitivity and glucose metabolism: ★★★★☆
✅ Safety: ★★☆☆ (broad biological activity; oncological risks require assessment)
⚠️ Possible sensations and side effects: hypoglycemia, edema, limb numbness; glucose monitoring mandatory
🤝 Combinations (goal → stack)
💪 Muscle growth + GH axis → IGF-1 LR3 + CJC-1295 DAC
🏋️ Recomposition + lean mass → IGF-1 LR3 + 5-Amino-1MQ
🔧 Muscle + tissue recovery → IGF-1 LR3 + BPC-157
| CAS Number | 946870-92-4 |
| Batch Purity | 98.46 % |
Full information in our guide
https://peptideboost.club/guide/igf-1lr3
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