Insulin‐like growth factor binding protein‐1 as glucose regulator in adolescent boys with type 1 diabetes

The aim of the present study was to investigate whether the diurnal variability of B‐Glucose is dependent on GH, IGF‐I and IGFBP‐I levels, apart from insulin, and if there is any difference between Tanner stages 3 and 5. Five boys in Tanner stage 3 and 6 boys in stage 5 with type 1 diabetes were included. Blood was continuously collected from a cubital vein for 24 h. S‐Insulin, S‐GH, S‐IGF‐I and S‐IGFBP‐1 were analysed. B‐Glucose was analysed hourly at bedside. One week before and 1 wk after the 24‐h study period the participants performed self‐monitoring of blood glucose (SMBG) during normal physiologic conditions. In the 24‐h profile of B‐Glucose, insulin, IGFBP‐I and GH, we found a significant positive correlation between B‐Glucose and log IGFBP‐1 (r=0.5, p= 0.005) and an inverse correlation to insulin (r=‐0.5, p= 0.004) but no correlation to logGH (r=‐0.04, p= 0.831). In multiple regression analysis, B‐Glucose was still significantly correlated to log IGFBP‐1, when adjusting for insulin and GH, in Tanner stage 5. We found a difference between Tanner stages 3 and 5 in the variability of B‐Glucose over a longer period during normal daily activity (p= 0.02), but not over the 24‐h study period. Conclusion: We have demonstrated in type 1 diabetes adolescent boys a relationship between simultaneously measured blood‐glucose and IGFBP‐1 levels independent of the insulin and GH levels, suggesting that the free fraction of IGF‐I influences the glucose metabolism.