IGF 1 LR3 (Insulin like Growth Factor 1 Long R3) is often called the "Holy Grail" of muscle building peptides because of its potent anabolic effects. In a Med Spa context, it is typically sought out IGF 1 vs. HGH Which is Better for Growth and Fat Loss? HRT Mechanisms of IGF 1 Mediated Regulation of Skeletal Muscle Hypertrophy and Atrophy IGF 1 LR3 1mg Maximum Muscle Growth & Performance Enhancement Attenuated glucose stimulated insulin secretion during an acute IGF 1 LR3 infusion into fetal sheep does not persist in isolated islets Journal of Developmental Origins of Health and Disease Cambridge Core