IGF 1 LR3 and Penis Enlargement: What the Evidence Actually Shows IGF LR3 is a peptide that play a role in muscle growth, tissue repair and recovery. But like all peptide therapies, it's not one size fits all. We focus on using peptides thoughtfully and in the IGF 1: Miracle Hormone or Health Hazard? Diet vs Disease What is IGF 1 LR3?, Insulin Like Growth Factor 1 Long R3 (IGF 1 LR3) is a modified version of IGF 1 with a longer half life, making it significantly more potent and effective for muscle growth,