IGF-I IS AVAILABLE AS MECASERMIN, A PRODUCT OF RECOMBINANT DNA TECHNOLOGY. THE SOMATOMEDINS ARE A GROUP OF POLYPEPTIDE HORMONES, SOME OF WHICH ARE INVOLVED IN MEDIATING THE EFFECTS OF GROWTH HORMONE IN THE BODY. IGF-I (MECASERMIN) IS BELIEVED TO BE RESPONSIBLE FOR MANY OF THE ANABOLIC EFFECTS OF GROWTH HORMONE. IT IS SECRETED PRIMARILY BY THE LIVER, REGULATED PRINCIPALLY BY GROWTH HORMONE AND INSULIN SECRETION; IGF-I MAY ALSO BE SECRETED IN OTHER TISSUES, WHERE IT MAY EXERT LOCAL HORMONAL (PARACRINE) EFFECTS. IN THE CIRCULATION, IGF-I IS ALMOST COMPLETELY PROTEIN BOUND; 6 BINDING PROTEINS HAVE BEEN IDENTIFIED AND PRODUCTION OF SOME OF THESE IS ALSO UNDER THE CONTROL OF GROWTH HORMONE. IN ADDITION TO ITS ANABOLIC EFFECTS IGF-I, WHICH IS STRUCTURALLY RELATED TO INSULIN, ALSO HAS POTENT HYPOGLYCAEMIC PROPERTIES.
INSULIN-LIKE GROWTH FACTOR-1 (IGF-1) IS THE PRINCIPAL HORMONAL MEDIATOR OF STATURAL GROWTH. UNDER NORMAL CIRCUMSTANCES, GROWTH HORMONE (GH) BINDS TO ITS RECEPTOR IN THE LIVER, AND OTHER TISSUES, AND STIMULATES THE SYNTHESIS/SECRETION OF IGF-1. IN TARGET TISSUES, THE TYPE 1 IGF-1 RECEPTOR, WHICH IS HOMOLOGOUS TO THE INSULIN RECEPTOR, IS ACTIVATED BY IGF-1, LEADING TO INTRACELLULAR SIGNALING WHICH STIMULATES MULTIPLE PROCESSES LEADING TO STATURAL GROWTH. THE METABOLIC ACTIONS OF IGF-1 ARE IN PART DIRECTED AT STIMULATING THE UPTAKE OF GLUCOSE, FATTY ACIDS, AND AMINO ACIDS SO THAT METABOLISM SUPPORTS GROWING TISSUES.