IGF 1 LR3 Huma Peptide IGF 1 LR3 does not promote growth in late gestation growth restricted fetal sheep American Journal of Physiology Endocrinology and Metabolism American Physiological Society 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, Effect of 6 weeks of treatment on serum IGF 1. Red bars represent Download Scientific Diagram Frontiers Sheep recombinant IGF 1 promotes organ specific growth in fetal sheep