It is a well-known fact that Insulin and IGF-1 are both critical hormonal regulators of muscle growth and homeostasis. However, a number of studies have additionally shown that the receptor for IGF-1, the IGF1-R, is expressed in significantly higher levels on muscle stem cells compared to the Insulin receptor. More importantly, results have furthermore demonstrated that IGF-1 is a more potent mitogenic regulator of primary myoblast and myotubes than Insulin. These results, together with unpublished results from in house studies, suggest that IGF-1 is a more important metabolic regulator of muscle growth than Insulin.