Growth Hormone, Insulin-Like Growth Factor-I and Insulin-Like Growth Factor Binding Protein-3 Are Regulated Differently in Small-for-Gestational-Age and Appropriate-for-Gestational-Age Neonates

Abstract

Growth hormone (GH), insulin-like growth factor-I (IGF-I) and IGF-binding protein-3 (IGFBP-3) were measured in 90 neonates during the first 5 days of life. Twenty-six small-for-gestational-age (SGA) neonates were compared with 64 appropriate-for-gestational-age (AGA) neonates. There were no differences in nutritional status between the 2 groups. Mean GH levels were significantly higher in the SGA group (53.4 ± 30.8 vs. 39.9 ± 23.3 µg/l; p < 0.05). In both groups GH levels correlated with birth weight (expressed as SDS) but not with gestational age. IGF-I levels were significantly lower in SGA neonates (6.6 ± 4.0 vs. 11.7 ± 8.2 ng/ml; p < 0.01). In SGA neonates with short stature, IGF-I levels were lower and GH levels were higher than in normal stature SGA neonates. IGFBP-3 levels were significantly lower in SGA neonates than in AGA neonates (0.72 ± 0.40 vs. 0.98 ± 0.43 µg/l; p < 0.01). IGF-I and IGFBP-3 correlated with gestational age in AGA but not in SGA neonates and there was no correlation with birth weight in either group. Our data provide evidence for a graduation in the severity of impact of fetal ‘malnutrition’ on the somatotropic axis and on intrauterine growth. The most severe state (SGA with short stature) was associated with a GH-resistance syndrome, characterized by very low IGF-I levels and high GH levels.