Insulin-like growth factor-1 also known as Somatomedin C is produced primarily in liver and serves as an endocrine (as well as paracrine and autocrine) hormone mediating the action of GH in peripheral tissues. Secretion of IGF-1 is stimulated by Growth Hormone after bih, and it has pronounced growth-stimulating activity required for both skeletal and Cailage growth. Feature Insulin IGF-I IGF-II Other names Insulin Somatomedin C Multiplication stimulating activity (MSA) Number of amino acids 51 70 67 Source Pancreatic beta cells liver and other tissues Diverse tissues Level regulated by Glucose Growth Hormone after bih. Nutritional status Unknown Plasma levels 0.3-2 ng/ml 10-700 ng/ml; Peaks at pubey 300-800 ng/mL Plasma binding proteins No Yes Yes Major Physiological Role Control of metabolism Skeletal and Cailage growth Growth during fetal development Ref: Ganong Pgno : 329