Serum concentrations of insulin, insulin-like growth factor(IGF)-I, IGF binding protein (IGFBP)-1 and -3 and growth hormone binding protein in obese children: fasting IGFBP-1 is suppressed in normoinsulinaemic obese children

Abstract

Objective: Simple obesity is characterized by normal or accelerated growth in the presence of reduced serum levels of GH, whereas its detailed mechanism remains unknown. We, therefore, evaluated interrelationships among serum levels of insulin, IFG-I, IGF binding protein (IGFBP)-1 and -3 and growth hormone binding protein (GHBP) in prepubertal obese children.

Subjects: Prepubertal 20 obese children and 20 age-matched control children were included in the study.

Results: Serum levels of insulin, IGF-I and IGFBP-3 in obese children did not differ from those in controls. The serum level of IGFBP-1 was significantly lower in obese children (22.1 +/- 18.4 micrograms/l, P < 0.001) than in control children (76.0 +/- 62.9 micrograms/l). No relationship was found between the serum levels of insulin and IGF-I, IGFBP-1, or IGFBP-3 in obese subjects. The serum level of GHBP in obese children was significantly elevated as compared with that in controls and was positively correlated with body mass index (BMI). No relationship was found between the serum levels of GHBP and IGF-I in obese subjects.

Conclusions: The present study showed for the first time that the fasting IGFBP-1 level was suppressed in prepubertal obese children with fasting normoinsulinaemia. We speculate that the hyperinsulinaemia which cannot be detected in the fasting state may have suppressed hepatic production of IGFBP-1. Alternatively, the reduced IGFBP-1 is likely to be a compensatory response to impaired insulin sensitivity. Thus, the IGFBP-1 level may be a useful predictor for the early identification in the development of insulin resistance in prepubertal obese children.