Objectives: To compare glucose tolerance and parameters of insulin sensitivity and β-cell function between chronic glucocorticoid (GC)-using and GC-naive patients with rheumatoid arthritis (RA).
Methods: Frequently sampled 75 g oral glucose tolerance tests were performed in 58 chronic GC-using and 82 GC-naive patients with RA with established disease, with no known type 2 diabetes mellitus (T2DM), and 50 control subjects of comparable age with normal glucose tolerance. The associations between cumulative GC dose and disease characteristics and glucose tolerance state, insulin sensitivity and β-cell function were tested using multivariate linear and logistic regression models, correcting for patient characteristics.
Results: Glucose tolerance state, insulin sensitivity and β-cell function did not differ between the two RA populations; de novo T2DM was detected in 11% and impaired glucose metabolism in 35% of patients with RA. In patients with RA, cumulative GC dose was associated with T2DM, which seemed mostly driven by the effects of cumulative GC dose on insulin resistance; however, the association decreased when corrected for current disease activity. Patients with RA had decreased insulin sensitivity and impaired β-cell function compared with controls, and multivariate regression analyses showed a negative association between the presence of RA and insulin sensitivity.
Conclusions: GC-using and GC-naive patients with RA had comparable metabolic parameters, and had decreased insulin sensitivity and β-cell function as compared with healthy controls. Although cumulative GC dose was shown to have a negative impact on glucose tolerance state and insulin sensitivity, confounding by indication remains the main challenge in this cross-sectional analysis.