IGF-1 LR3 — Long R3 Insulin-like Growth Factor 1

What Is IGF-1 LR3?

IGF-1 LR3 is a modified version of insulin-like growth factor 1 with an extended half-life. The 'Long R3' modification replaces glutamic acid at position 3 with arginine and adds 13 amino acids to the N-terminus, dramatically reducing IGF-binding protein affinity. This results in a half-life of approximately 20-30 hours compared to ~20 minutes for native IGF-1.

Mechanism of Action

IGF-1 LR3 activates the IGF-1 receptor, triggering the PI3K/Akt and MAPK/ERK signaling cascades. These pathways promote protein synthesis, cell proliferation, and inhibit apoptosis. Its reduced binding protein affinity means more free IGF-1 LR3 is available to activate receptors, making it significantly more potent than native IGF-1 on a per-dose basis.

Key Research Findings

• Muscle hypertrophy — Cell culture and animal studies demonstrate enhanced muscle fiber growth and satellite cell activation
• Recovery — Accelerated recovery from muscle damage in preclinical models
• Metabolic effects — Glucose uptake and utilization similar to insulin at high concentrations
• Cell proliferation — Potent mitogenic effects across multiple tissue types
• Extended activity — 20-30 hour half-life provides sustained anabolic signaling

Known Side Effects

Hypoglycemia is a significant risk due to insulin-like activity. Other concerns include joint pain, edema, potential for organ growth (organomegaly) with sustained use, and theoretical oncological risk due to proliferative signaling. This compound requires careful dosing consideration.

Legal Status (2026)