β-cell function and insulin sensitivity contributions on incident diabetes in patients with endogenous Cushing’s syndrome

Abstract

ObjectiveTo evaluate the relative contributions of β-cell function and insulin sensitivity on the deterioration of glucose tolerance from OGTT in patients with endogenous CS. MethodsWe retrospectively analyzed the data of 60 patients with CS and determined the glucose metabolism and β-cell function through OGTT. Their general characteristics were retrieved. A series of parameters for assessing insulin sensitivity and β-cell function was calculated. The logistic regression model was used to investigate insulin sensitivity and β-cell function contributions on incident diabetes. ResultsOf the 60 patients with CS, 10 (16.7%), 21 (35%), and 29 (48.3%) were classified as CS/ normal glucose tolerance (NGT), CS/prediabetes, and CS/diabetes mellitus (DM). Compared with the HCs, the CS/NGT patients had higher HOMA-IR and lower ISI-Matsuda but with a compensatory increase in HOMA-β. Significant decreasing trends were observed in HOMA-β, AUCI/G and ΔI30/ΔG30 among CS/NGT, CS/prediabetes and CD/DM groups. The OR of incident diabetes compared with the high AUCI/G/high ISI group was significant in the low AUCI/G/high ISI group. ConclusionImpairment of the β-cell function had a more profound effect on incident diabetes than decreased insulin sensitivity. An approach based on an OGTT has utility for diagnosing dysglycaemia and β-cell dysfunction in patients with CS.