Serum levels of free insulin-like growth factor (IGF)-I and IQF-binding protein-1 in prepubertal children with idiopathic short stature

OBJECTIVE The study was performed to evaluate the relationships among serum free and total insulin-like growth factor (IGF)-I, IGF-binding protein-1 ( IGFBP-1), IGFBP-3, and insulin concentrations in prepubertal children with idiopathic short stature (ISS). SUBJECT Eighteen children with ISS and 15 age-matched controls were include d in the study. All short children had a height standard deviation score of more than 2 below the mean, and maximum stimulated GH levels greater than 10 mug/l after two standard provocation tests. RESULTS The serum levels of free IGF-I were significantly lower in short ch ildren (1.6 +/- 0.3 mug/l) than in the controls (2.8 +/- 0.6 mug/l, P < 0.0 5), while total IGF-I levels were slightly, but not significantly, lower In short children than in controls. The serum levels of IGFBP-1 were signific antly higher in the ISS group(124.6 +/- 5.6 <mu>g/l) than in controls (80.0 +/- 8.7 mug/ I, P < 0.0001). The fasting insulin and IGFBP-3 levels were s imilar in both groups. A stepwise regression analysis for all subjects reve aled that IGFBP-1 is the only independent predictor of log free IGF-I (R-2 = 0.23, P < 0.01). CONCLUSIONS The present study shows that the serum levels of free IGF-1 are significantly lower and insulin-like growth factor-binding protein-1 level s are higher in prepubertal children with idiopathic short stature, as comp ared with age-matched controls. The high IGFBP-1 may contribute to growth r etardation in a subgroup of idiopathic short stature through a decrease in free IGF-1.