Modulatory activity of testosterone on growth pattern and IGF 1 levels in vanishing testis syndrome: a case report during 15 years of follow up BMC Endocrine Disorders Springer Nature Link If your priority is building muscle, IGF 1 is what really matters. Recombinant Human LR3 IGF I IGF 1 GMP Protein, CF 8335D GMP: R&D Systems 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 IGF 1 LR3 1mg Insulin Like Growth Factor