About IGF-1 LR3
IGF-1 LR3 (Long R3 Insulin-like Growth Factor 1) is a synthetically modified 83-amino acid analog of human IGF-1. The modification consists of an arginine substitution for glutamic acid at position 3, combined with a 13-amino acid extension at the N-terminus. Together, these changes dramatically reduce the peptide's binding affinity for IGF-binding proteins (IGFBPs) — proteins that, in their native form, sequester roughly 95–99% of circulating IGF-1 and limit its bioavailability and half-life to just minutes.
By minimizing IGFBP binding, IGF-1 LR3 extends its biological half-life to an estimated 20–30 hours, allowing far more free, bioactive peptide to remain in circulation. Research interest centers on its activation of the IGF-1 receptor, which triggers the PI3K/Akt/mTOR signaling pathway — a cascade strongly associated with increased protein synthesis. Of particular note, IGF-1 LR3 is studied for its potential to stimulate satellite cell proliferation, a process linked to muscle fiber hyperplasia (the formation of new muscle fibers) rather than just hypertrophy of existing fibers, as well as effects on fat metabolism and body recomposition.
Research Applications
IGF-1 LR3 is used in research investigating muscle hypertrophy and hyperplasia, satellite cell activation, protein synthesis pathways (PI3K/Akt/mTOR), fat metabolism, and body recomposition. It is also studied alongside growth-hormone secretagogues to examine downstream IGF-1 receptor signaling independent of pituitary GH output.