IGF-1LR3

What is IGF-1 LR3?

IGF-1 LR3 (Long Arginine 3-IGF-1) is a synthetic analogue of human Insulin-Like Growth Factor 1 with an N-terminal extension and an Arg-for-Glu substitution at position 3. These modifications dramatically reduce its affinity for IGF-binding proteins (IGFBPs) — proteins that normally sequester IGF-1 in the bloodstream and limit its bioavailability. This results in a compound with approximately 3-fold greater potency than native IGF-1 and an extended half-life of 20-30 hours (vs. 12-15 minutes for native IGF-1).

Mechanism of Action

IGF-1 Receptor Agonism

IGF-1 LR3 activates the IGF-1 receptor (IGF-1R) with equivalent affinity to native IGF-1 — triggering the full downstream signaling cascade: PI3K-Akt-mTOR (muscle protein synthesis, cell survival) and MAPK-ERK (cell proliferation, differentiation).

IGFBP Resistance

The key modification: native IGF-1 is 97-99% bound to binding proteins in circulation, leaving only 1-3% free and bioavailable. IGF-1 LR3's reduced IGFBP affinity means a far greater proportion remains free and active — producing sustained receptor engagement throughout its 20-30 hour half-life.

Systemic Anabolic Effects

IGF-1's downstream effects include increased muscle protein synthesis, satellite cell activation, adipose lipolysis, bone density enhancement, and connective tissue anabolism — making IGF-1 LR3 relevant to body composition, recovery, and musculoskeletal research.

Key Research Findings

Research demonstrates IGF-1 LR3's superior potency in muscle protein synthesis assays compared to native IGF-1. In animal models, it drives significant lean mass accretion, accelerated injury recovery, and improved bone density. The extended half-life allows once-daily dosing to maintain meaningful IGF-1R activation throughout the day.

*For research use only. Not for human consumption.*