Association of glucocorticoid receptor polymorphism A3669G with decreased risk of developing diabetes in patients with Cushing's syndrome

ObjectiveGlucocorticoid receptor (GR) polymorphisms alter glucocorticoid (GC) sensitivity and have been associated with altered metabolic profiles. We evaluate the prevalence of the fourGR(NR3C1) polymorphisms BclI, N363S, ER22/23EK, and A3669G in patients with Cushing's syndrome (CS) compared with healthy controls (HC) and we investigate their role in the development of metabolic abnormalities in patients with CS according to their hormonal profile.Patients and methodsSixty-one patients with CS and 71 sex- and age-matched HC were genotyped.ResultsBclI variant was markedly higher in patients with CS compared with HC (62 vs 41%,PIn CS patients, despite the significantly increased levels of morning serum cortisol in BclI carriers compared with wild type no clinical or metabolic differences were found.In contrast, A3669GGRcarriers showed a significantly reduced prevalence of type 2 diabetes mellitus compared with wild type (19 vs 68%,P=0.001) despite the higher levels of both serum morning (21.7±6 vs 27.3±8.6 μg/dl,P=0.009) and midnight cortisol (18.8±5.8 vs 24.0±8.0 μg/dl,P=0.01). The negative association between diabetes and A3669GGRpolymorphism remained significant when data were adjusted for potential confounding factors.ConclusionsThe A3669G polymorphism of theGRgene plays a protective role in patients with CS, attenuating the effects of GC excess on glucose metabolism as shown by their reduced risk of diabetes.