IGF 1 LR3 The Muscle Building Peptide Everyone's Talking About IGF 1 LR3 is one of the most powerful performance peptides used for muscle growth, recovery, and fat loss. It's 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) Organ weights in response to Long R3 insulin like growth factor 1 (LR3 Download Scientific Diagram Localized Igf 1 transgene expression sustains hypertrophy and regeneration in senescent skeletal muscle Nature Genetics