Serum Insulin-like Growth Factor-I (IGF-I) and IGF Binding Protein-3 (IGFBP-3) in Growing Preterm Infants on Enteral Nutrition

We analyzed the range of serum concentrations of insulin-like growth factor-I (IGF-I) and insulin-like growth factor binding protein-3 (IGFBP-3) and their inter-relationships with age and some parameters of nutritional and hormonal status in 46 growing preterm infants on enteral nutrition. 72 nutritional balances were performed, with a cross-sectional study design, at a mean age of 35.3 +/- 17.2 days, equivalent to a mean corrected age (gestational + postnatal age) of 36 +/- 2.3 weeks. Serum concentrations of IGF-I (mean 64 +/- 36 ng/ml) and IGFBP-3 (mean 1.15 +/- 0.53 mg/l) correlated significantly with each other (r = 0.46) and both correlated with body weight (r = 0.43 and 0.34), body length (r = 0.44 and 0.36) and serum concentrations of prealbumin, apolipoprotein A and cholesterol. IGF-I also correlated with urinary excretion of C-peptide (r = 0.32). There was a weak correlation between IGFBP-3 and postnatal age (r = 0.36) but no correlation between IGF-I and IGFBP-3 and correlated age or urinary excretion of growth hormone. In growing preterm infants, at least until 40 weeks of corrected age, serum concentrations of IGF-I and IGFBP-3 seem to be related principally to body weight, body length and nutritional factors, but not to growth hormone.