IGF 1 LR3 and Penis Enlargement: What the Evidence Shows for Adult Men IGF 1 LR3 tells your muscle cells to grow, repair, and absorb nutrients better. It works directly at the muscle level to help you build lean muscle and recover faster.What it is IGF 1 IGF 1 LR3 and Penis Enlargement: What the Evidence Actually Shows IGF 1 LR3 does not promote growth in late gestation growth restricted fetal sheep American Journal of Physiology Endocrinology and Metabolism American Physiological Society IGF 1LR3 Advanced Anabolic Signaling & Muscle Growth