Stronger association between morning serum cortisol level and diurnal time in range in type 2 diabetes?

Abstract

Background: The hypothalamic-pituitary-adrenal axis is thought to play a vital role in glucose homeostasis and diabetes. This study investigated the association between morning serum cortisol and time in range (TIR), including daytime TIR, in type 2 diabetes (T2DM).

Methods: 310 patients with T2DM had serum cortisol measured at 8 a.m. All participants underwent continuous glucose monitoring (CGM) for three consecutive days, then TIR and glycemic variability (GV) parameters were evaluated. Using 100 g standard steamed bread meal test, blood glucose, C peptide and insulin at different points were collected to assess insulin sensitivity and islet function.

Results: Patients with higher serum cortisol exhibited lower TIR and TITR (P < 0.001). Spearman correlation analysis showed that the negative correlation between cortisol and daytime TIR (r=-0.231, P < 0.001) was stronger than that of overnight TIR (r=-0.134, P = 0.028). Similarly, there existed a negative correlation between cortisol and pancreatic function indicators such as HOMA-β, insulinogenic index (IGI), area under the curve of C-peptide within half an hour (AUCCp0.5 h) and three hours (AUCCp3h) (r=-0.248, -0.176, -0.140, -0.185, respectively, P < 0.05). In contrast, cortisol was positively associated with TAR (r = 0.217, P < 0.001) and GV parameters including MBG, MAGE, LAGE, HBGI, MODD, ADDR (P of MAGE and MODD > 0.05). Multiple stepwise regression revealed that cortisol was an independent contributor of TIR, TITR and diurnal TIR, with diurnal TIR of stronger relevance.

Conclusions: Morning serum cortisol is negatively correlated with TIR, especially diurnal TIR and positively associated with GV parameters. Inappropriate cortisol secretion may have an adverse influence on glucose homeostasis in T2DM.