Protein anabolic action of insulin, growth hormone and insulin-like growth factor I

Insulin, growth hormone (GH), insulin-like growth factor I (IGF-I), thyroid hormones, sex steroids, glucocorticoids, glucagon and catecholamines all influence protein metabolism and the response to physiological or pathological processes. Of these, insulin, IGF-I and GH play a dominant role in the day-to-day regulation of protein metabolism (see Refs 24, 72, 85 and 140). It is clear that these peptide hormones work in a coordinated and interdependent manner that is just beginning to be understood. The outcome in many pathological states is closely related to the balance of anabolic and catabolic processes. With a better understanding of the regulation of these processes, together with the newly available recombinant hormones, it will hopefully be possible to make therapeutic and clinical advances in the near future. The general principles of measuring protein metabolism and the role of each of these hormones in the regulation of protein metabolism are discussed below.