Association of midnight serum cortisol level with glucose metabolism and islet β cell function in newly-diagnosed diabetic patients

Objective To investigate the influence of the level of midnight serum cortisol on glucose metabolism and islet β cell function in newly-diagnosed untreated patients with type 2 diabetes mellitus (T2DM).Methods Serum cortisol at midnight and the following 8:00 Am,fructosamine (FA),areas under curve (AUC) of blood glucose and insulin during oral glucose tolerance test(OGTT) were determined in 180 cases[age (56.1 ± 11.8) y,male:86,female:94]of untreated T2DM,which were compared with 130 healthy persons.Results The levels of serum cortisol at midnight and the following 8:00 Am were significantly higher than those of control group[8:00(956.34±334.72 vs 579.43±83.86)nmol/L,0:00(316.20±248.20 vs 169.34±38.53)nmal/L,P＜0.01].Partial correlation analysis showed that the level of midnight cortisol was positively correlated with FA(r=0.38,P= 0.001) and AUC of OGTF(r =0.43,P＜0.001),and was negatively correlated with AUC of insulin release(r=-0.52,P＜0.001).Conclusion The raised cortisol level during midnight in untreated patients with T2DM was related with the dysfunction of β cell and uncontrolled hyperglycemia. Key words: Diabetes mellitus，type 2; Midnight cortisol; Fructosamine; β Cell function of islet