What is IGF-1? (Peptide Glossary)

IGF-1 is a 70-amino-acid protein produced primarily by the liver in response to growth hormone. It is the principal mediator of GH's anabolic and growth-promoting effects: when growth hormone is released, much of what happens next happens through IGF-1 signaling at the IGF-1 receptor, activating the PI3K/Akt/mTOR pathway studied extensively in muscle and cell-growth research.

Native IGF-1 has a half-life of only about 15 minutes because binding proteins (IGFBPs) sequester it rapidly. The research compound IGF-1 LR3 was engineered to escape this: an Arg3 substitution plus a 13-residue N-terminal extension reduces binding protein affinity, extending its research half-life to 20-30 hours. This makes LR3 a fundamentally different research tool from native IGF-1.

IGF-1 LR3 is a recombinant protein requiring expression-system manufacturing, not simple peptide synthesis - it is expensive to produce legitimately and a known target for substitution scams. Vials are small (0.1-1mg) because research doses are microgram-range. A vendor selling large, cheap IGF-1 LR3 vials warrants serious skepticism.