IGF-I, IGF-II, FREE IGF-I AND IGFBP-1, -2 AND -3 LEVELS IN VENOUS CORD-BLOOD - RELATIONSHIP TO BIRTH-WEIGHT, LENGTH AND GESTATIONAL-AGE IN HEALTHY NEWBORNS

The insulin-like growth factors (IGF-I and IGF-II) and their binding p roteins (IGFBPs) have been implicated in regulating fetal growth and d evelopment. The aim of this study was to determine whether fetal IGFs correlate with auxologic data at birth and/or gestational age. Venous cord blood was obtained from 138 healthy newborns immediately after bi rth and clinical data were recorded using a standardized data sheet. F or the determination of IGF-I and IGF-II, IGFBP-blocked radioimmunoass ays were used, A coated-tube immunoradiometric assay was applied for t he measurement of free IGF-I. IGFBP-1, -2, and -3 were measured using specific radioimmunoassays. IGF-I levels were 61 +/- 21 ng ml(-1), med ian 61 ng ml(-1), range 19-114 ng ml(-1); IGF-II levels were 466 +/- 8 0 ng ml(-1), median 457 ng ml(-1), range 311-701 ng ml(-1); free IGF-I levels were 2.4 +/- 1.8 ng ml(-1), median 1.8 ng ml(-1), range 0.4-7. 8 ng ml(-1). The concentration of IGFBP-1 was 144 +/- 110 ng ml(-1), m edian 113 ng ml(-1), range 20-626 ng ml(-1); that of IGFBP-2 was 1165 +/- 455 ng ml(-1), median 1119 ng ml(-1), range 440-3466 ng ml(-1). IG FBP-3 levels were 1272 +/- 280 ng ml(-1), median 1272 ng ml(-1), range 600-1966 ng ml(-1). IGF-I levels correlated significantly with IGFBP- 3 levels (r = 0.71), birthweight (r = 0.48) and birth length (r = 0.37 ). There were significant inverse correlations between IGF-I and both IGFBP-1 (r = -0.45) and IGFBP-2 (r = -0.62). Although free IGF-I level s correlated (r = 0.71) with total IGF-I, only marginally significant correlations were found between free IGF-I and birthweight (r = 0.25). According to multiple regression analysis free IGF-I levels were only dependent upon total IGF-I, IGFBP-2 and IGFBP-1, whereas IGFBP-3 leve ls did not contribute to the variance of free IGF-I concentrations in venous cord blood. There was no significant correlation between IGF-II and auxologic data at birth. When IGF-I and IGFBP-3 levels were analy sed with respect to gestational age a biphasic pattern with maxima at 270 d was observed. IGFBP-2 exhibited a reversed pattern with a minimu m at 265 d of gestation. In conclusion, these data suggest that IGF-I and the IGFBPs, but not IGF-II, play a role in the regulation of late fetal growth and development.