IGF 1 LR3 and Penis Enlargement: What the Evidence Actually Shows 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 How IGF 1 and MGF drive muscle growth after training Gabriel Alizaidy, MD, MS posted on the topic LinkedIn IGF 1 LR3 does not promote growth in late gestation growth restricted fetal sheep American Journal of Physiology Endocrinology and Metabolism American Physiological Society