IGF1 and Hyperinsulinemia: Different mechanisms have been proposed to explain the effects of nutritional repletion on GH secretion, including increase in free fatty acid (FFA) concentrations [51,52], alterations in hypothalamic somatostatin and GHRH secretion [14], modification of IGF-I bioavailability by changes in IGFBP concentrations [15,53,54,55], and hyperinsulinemia-mediated inhibition of GH secretion [50,56,57].