Correlation between cortisol and insulin-like growth factor-binding proteins (IGFBPs) under physiological conditions in children

OBJECTIVE A positive correlation between 24-h spontaneous growth hormone (G H) and cortisol secretion was previously reported in children. this observa tion prompted us to examine the relationship between physiological diurnal cortisol variation and the levels of insulin-like growth factors (IGFs) and IGF-binding proteins (IGFBPs) under physiological conditions. DESIGN AND PATIENTS Starting at 0800 h, blood was sampled every 20 minutes over 24 h for measurement of GH and cortisol concentration in nine non-GH-d eficient boys as part of a protocol for the investigation of short stature. MEASUREMENTS IGFBP-1 and insulin were measured in samples drawn every 4 h o ver the 24-h period while IGF-I, IGF-II, IGFBP-2 and IGFBP-3 were determine d in samples collected at the end of the study. RESULTS No correlation was observed between IGF-I or IGF-II and mean cortis ol levels. IGFBP-1 concentrations showed a marked circadian variation that was superimposed on the circadian rhythm for cortisol while a significant p ositive correlation was found for single point measurements between IGFBP-1 concentrations and cortisol levels measured in the same sample (r = 0.53) or at the preceding 20 minutes (r = 0.43), 40 minutes (r = 0.47) and 2 h (r = 0.38), suggesting an interplay between cortisol and IGFBP-1. A negative correlation (r= - 0.54) was found between IGFBP-1 and insulin levels determ ined in the same sample. A negative correlation (r= - 0.93) was also found between IGFBP-2 levels and mean cortisol concentrations during the precedin g 12 h, No correlation was observed between plasma IGFBP-3 measured by IRMA and mean cortisol levers, CONCLUSION Our data indicate a clear correlation between cortisol and IGFBP -1 and IGFBP-2 levels. Thus, the interplay of spontaneous GH and cortisol s ecretion in children may involve changes in IGFBP-1 and IGFBP-2 levels.