IGF-1 LR3 — Ireland Research Reference Guide (2026)

By the Peptides Lab Ireland research team · Updated July 2026 · Research use only

IGF-1 LR3 (Long R3 IGF-1) is a modified insulin-like growth factor 1 analogue with an extended half-life and reduced binding-protein affinity and properties that make it the most heavily used IGF-1 research reference. This guide is for Irish research groups working with IGF-1 LR3 in preclinical protocols.

What is IGF-1 LR3?

IGF-1 LR3 is a synthetic 83 amino acid analogue of endogenous IGF-1 (which is 70 amino acids). Two modifications distinguish it from native IGF-1:

• Arg → Glu substitution at position 3 (the “R3”) , reduces affinity for IGF-binding proteins (IGFBPs)
• 13 amino acid N-terminal extension (the “L” for Long) — further reduces IGFBP binding and extends half-life

Combined, these modifications increase circulating half-life ~3× vs native IGF-1 and increase apparent bioavailability by displacement from binding proteins.

IGF-1 LR3 vs native IGF-1 in research

Research applications

• IGF-1 receptor pharmacology and sustained receptor engagement studies
• Protein synthesis research — mTOR pathway activation in muscle biology
• Satellite cell activation — skeletal muscle regeneration research
• Chondrocyte biology , cartilage and growth plate research
• Cellular proliferation research IGF-1R-mediated cell cycle studies
• Comparative studies vs MGF, PEG-MGF, and full-length HGH 191AA

Reconstitution reference

IGF-1 LR3 reconstitutes with bacteriostatic water using the standard technique , see our reconstitution guide. As a modified protein (not a small peptide), gentle handling is essential — swirl only, don’t shake.

Related research compounds

• IGF-DES — truncated des(1-3) IGF-1 analogue (also reduced IGFBP binding, different half-life)
• MGF , Mechano Growth Factor (IGF-1Ec splice variant)
• PEG-MGF — pegylated extended-half-life MGF
• HGH 191AA upstream reference in the GH → IGF-1 axis

Sourcing IGF-1 LR3 in Ireland

Peptides Lab Ireland stocks HPLC-verified IGF-1 LR3 with per-batch Certificate of Analysis. See the product page.

Continue on the topic

• Muscle Growth research peptides category
• Ipamorelin + CJC-1295 Research Reference
• Follistatin and Myostatin Pathway
• Reconstitution guide

For laboratory research use only. Not intended for human or veterinary use.