IGF 1 LR3 The Muscle Building Peptide Everyone's Talking About IGF 1 LR3 is one of the most powerful performance peptides used for muscle growth, recovery, and fat loss. It's a modified version Recombinant Human LR3 IGF 1(E51R) Protein Insulin like growth factor 1 stimulates retinal cell proliferation via activation of multiple signaling pathways ScienceDirect Insulin like growth factor 1 promotes cell cycle progression via upregulation of cyclin D1 expression through the phosphatidylinositol 3 kinase nuclear factor B signaling pathway in FRTL thyroid cells Acta Pharmacologica Sinica