IGF 1 LR3 The Muscle Building Peptide Everyones Talking About , IGF 1 LR3 is one of the most powerful performance peptides used for muscle growth, recovery, and fat loss. Its a modified version IGF1 stimulates greater muscle hypertrophy in the absence of myostatin in male mice in: Journal of Endocrinology Volume 234 Issue 2 (2017) Local application of engineered insulin like growth factor I mRNA demonstrates regenerative therapeutic potential in vivo ScienceDirect IGF 1 infusion to fetal sheep increases organ growth but not by stimulating nutrient transfer to the fetus American Journal of Physiology Endocrinology and Metabolism American Physiological Society