Researchers can't fully explain why IGF LR3 outperforms its natural counterpart in preclinical models. Engineered in the 1990s with an arginine substitution and N terminal extension, this synthetic IGF 1 analog shows reduced IGFBP binding A Medical Review of IGF 1 LR3 Dosage, Side Effects and Safety Aspects IGF 1 LR3 Peptyds Insulin like growth factor 1 deficiency and metabolic syndrome Journal of Translational Medicine Springer Nature Link