If your priority is building muscle, IGF 1 is what really matters. IGF 1 LR3 Peptide Affect Serum Insulin like Growth Factor 1 Is a Biomarker of Testosterone Production and Intact Acrosome in Asian Elephants (Elephas maximus) 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 IGF 1 LR3 1MG Research Peptide Laboratory Study