RESUMO
BACKGROUND: Insulin-like growth factor-I (IGF-I) and insulin are structurally related proteins with similar receptors and signal transduction systems. AIM: We postulate that some low birth weight (LBW) children may have decreased sensitivity to both insulin and IGF-I. METHODS: We studied 48 prepubertal LBW children aged 7.6 +/- 2.4 years. Insulin sensitivity was determined using an oral glucose tolerance test, and IGF-I sensitivity was assessed by determining nocturnal GH concentrations at baseline and after administration of recombinant human IGF-I/IGFBP-3 complex. RESULTS: Children were classified into quartiles of insulin sensitivity based on their glucose AUC/insulin AUC index. Children in the lowest quartile of insulin sensitivity exhibited a lower IGF-I sensitivity after administration of the rhIGF-I/rhIGFBP-3 complex compared to children in the highest quartile of insulin sensitivity (percent change in GH AUC: -44.2 +/- 5.7 vs. -21.6 +/- 6.8, p < 0.05). CONCLUSION: LBW children in the lowest quartile of insulin sensitivity exhibited a lower pituitary GH response to the administration of rhIGF-I/rhIGFBP-3. Our findings suggest that reduced sensitivity to insulin and IGF-I may coexist in some prepubertal LBW children.