IGF-1, stimulated by GH, is synthesized and secreted in the liver, and is also produced in target tissues in both autocrine and paracrine modes. How does IGF-1 promote anabolic effects in bodybuilding? IGF-1 works by binding to the IGF-1 receptor, and before binding to the IGF-1 receptor, IGF-1 is transported to various parts of the body via IGF-binding proteins. Before …