Effects of recombinant human insulin-like growth factor I administration in adults with growth hormone deficiency

Recombinant human insulin-like growth factor I (IGF-I), 40 μg/kg/body weight, was administered subcutaneously at 08.00 hours to six adult patients with growth hormone deficiency (GHD). The mean maximal IGF-I concentrations were found 2–6 hours after injection. Concentrations then gradually declined, though mean values were still above basal 24 hours after the injection. Only one patient maintained IGF-I levels above the lower normal range throughout 24 hours. There was a significant decrease in mean IGF-II concentrations when measured 4 and 24 hours after injection of IGF-I. The diurnal variations of insulin and IGF binding protein-1 were preserved. There were no side-effects, and blood glucose remained normal. These results show that in patients with low IGF-I levels resulting from GHD, it is necessary to administer IGF-I at intervals of less than 24 hours to obtain IGF-I levels that are within the normal range.