IGF 1 LR3: Nasal Spray vs. Subcutaneous Injection Comparison IGF 1 LR3 Supra Chems IGF 1 LR3 Overwatch Research 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 IGF 1 LR3 does not promote growth in late gestation growth restricted fetal sheep American Journal of Physiology Endocrinology and Metabolism American Physiological Society