IGF-1 LR3
Dosage Protocol
IGF-1 LR3 (Long Arg3 IGF-1) is a synthetic analog of insulin-like growth factor-1 with an arginine substitution at position 3 and an N-terminal 13-amino acid extension. These modifications drastically reduce IGF-binding protein (IGFBP) affinity, extending the half-life from ~12 minutes (native IGF-1) to approximately 20–30 hours and increasing free, bioactive IGF-1 levels.
What is IGF-1 LR3?
Native IGF-1 has a plasma half-life of only ~10–12 minutes due to rapid binding by insulin-like growth factor binding proteins (IGFBPs 1–6). IGF-1 LR3 was engineered with an Arg3 substitution and 13-amino acid N-terminal extension that dramatically reduces IGFBP affinity by >1000-fold, allowing the peptide to remain in free, receptor-active form for 20–30 hours after injection.
IGF-1 LR3 activates IGF-1 receptors (IGF1R) throughout the body — stimulating muscle protein synthesis, satellite cell activation and proliferation, glucose uptake, and adipocyte apoptosis. Its systemic distribution distinguishes it from IGF-1 DES, which has more localized site-specific action. It is prohibited by WADA and represents a significant anabolic compound in sports doping research.
Dosing Schedule
Parameters documented in published preclinical and clinical research.
| Phase | Dose | Frequency | Duration | Notes |
|---|---|---|---|---|
| Start | 20–40 mcg | Post-workout SubQ/IM | Days 1–7 | Assess glucose response. Post-workout timing with food to manage hypoglycemia risk. |
| Working dose | 40–80 mcg | Once daily | Weeks 1–4 | Post-workout or AM. Max 4-week cycles to prevent receptor desensitization. |
| Advanced | 80–100 mcg | Once daily | Weeks 1–4 | Upper research dose. Hypoglycemia risk increases — have glucose available. |
| Off cycle | — | — | 4 weeks minimum | Equal on/off cycling essential to prevent IGF1R downregulation. |
Safety & Side Effects
Academic References
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[1]
Francis GL, et al. (1992). Insulin-like growth factors 1 and 2 in bovine colostrum. Biochem J. 251(1):95–103. PubMed ↗
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[2]
Tomas FM, et al. (1993). Prolonged effects of insulin-like growth factor-I (IGF-I) and truncated IGF-I on tissue growth and glucose metabolism in pigs. J Endocrinol. 137(3):413–21. PubMed ↗
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[3]
Girbau M, et al. (1987). Insulin and insulin-like growth factor I both stimulate metabolism, growth, and differentiation in cultured sympathoadrenal progenitor cells. Proc Natl Acad Sci USA. 84(9):2892–6. PubMed ↗
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[4]
Baserga R. (1994). The insulin-like growth factor I receptor: a key to tumor growth? Cancer Res. 55(2):249–52. PubMed ↗