INSULIN-LIKE-GROWTH-FACTOR AXIS PARAMETERS IN SICK HOSPITALIZED NEONATES

The circulating insulin-like growth factor (IGF) axis consists of the IGF peptides, the IGF binding proteins (IGFBPs), and the IGFBP proteas es. Little is known about the IGF axis in newborns, its possible pertu rbations in sick neonates, and the effect of nutrition on the IGF axis of such patients, The aims of this study were to define IGF axis para meters in the sera of hospitalized newborns and to correlate these par ameters with the nutritional status of the infants, Serum samples obta ined from twenty four hospitalized infants in the intensive care nurse ry were analyzed for IGF axis parameters. Insulin-like growth factor-I and IGFBP-3 by RTA were mostly within the normal range for age and we re only minimally affected by gestational age. In comparison, 8 newbor n infants with congenital growth hormone deficiency had IGFBP-3 levels which were below the normal range, Two infants on ECMO had elevated l evels of IGFBP-3 by RIA, Western ligand blotting (WLB) demonstrated th at IGFBP-2 was the major binding protein in infant serum and the 44 kD a IGFBP-3 in critically ill neonatal serum was approximately 10% of ad ult serum levels, IGFBP-3 by RIA in neonatal serum averaged approximat ely 25% of adult serum levels. Compatible with this discrepancy, a num ber of sick neonates had detectable levels of IGFBP-3 proteolytic acti vity and higher levels of IGFBP-3 fragments compared to normal adult s erum in both the protease assays and Western immunoblotting, There was no correlation between any IGF axis parameter and nutritional status. In summary, sick hospitalized neonates display mostly normal IGF and IGFBP-3 levels, which are not correlated to nutritional intake. Thus s erum IGFBP-3 levels maintain their diagnostic utility for growth hormo ne deficiency in critically ill neonates.