IGF-1 LR3

Overview

IGF-1 LR3 is a modified form of insulin-like growth factor-1 with an extended half-life due to a 13-amino acid N-terminal extension and an arginine substitution at position 3. It is studied for its potent anabolic effects on skeletal muscle, including hyperplasia (new muscle fiber formation).

Mechanism of Action

IGF-1 LR3 binds to IGF-1 receptors on muscle cells with reduced affinity for IGF binding proteins, resulting in higher circulating bioactive IGF-1. It activates the PI3K/Akt/mTOR pathway, promoting muscle protein synthesis, satellite cell activation, and inhibition of protein degradation. Unlike native IGF-1, its reduced IGFBP binding extends its biological half-life to 20–30 hours.

Research Summary

Preclinical studies demonstrate significant muscle hypertrophy and hyperplasia, improved nitrogen retention, and enhanced recovery from muscle damage. IGF-1 LR3 is widely studied in muscle biology and cachexia research. It is banned by WADA and classified as a prohibited growth factor in competitive sports.

Dosing Information

Reported Side Effects

• Hypoglycemia
• Joint pain
• Jaw growth and extremity swelling (prolonged use)
• Injection site irritation
• Gut distension (high doses, prolonged use)

Research References

• Insulin-like growth factor-I and its binding proteins: regulation and biological actions (1997)
• Long R3 IGF-I enhances muscle protein synthesis and reduces degradation in vivo (2001)
• IGF-I and muscle growth: role of IGF-I and its binding proteins in the control of myogenesis (2004)