Evaluation of the relationship between glucose metabolism disorder and thyroid volume

Functional and morphological alterations of the thyroid gland generated by insulin resistance and related metabolic disturbances constitute the hot agenda of the Endocrine research recently. Impaired Fasting Glucose (IFG), Impaired Glucose Tolerance (IGT) and Diabetes Mellitus (DM) are basic disorders of glucose metabolism in which insulin resistance plays a prominent role. The present case-control study aimed to investigate the changes in thyroid volume and nodule prevalence in patients with disturbed glucose metabolism. Patients with IFG and IGT were grouped as prediabetes (n=250). The other two groups were Type 2 DM (n=141) and a control group (n=261) which consisted of cases with no known glucose metabolism disturbance. All of the patients were recently diagnosed. Body weight, waist circumference, serum TSH levels of all cases were measured. A single operator performed thyroid ultrasonography to all participants. The mean TSH value was found to be significantly higher in DM group than the other two groups (mean TSH of DM group was 1,87±0,9 mIU/ml; that of prediabetes group was 1,49±0,8 mIU/ml and that of the control group was 1,47±0,8 mIU/ml; p<0,001). Mean thyroid volume was significantly different from each other in all groups. It was significantly higher in prediabetics than the control group (18,8±9,0 and 12,8±4,2 ml, respectively), in DM group than the prediabetic group (20,6±8,7 and 18,8±9,0 ml, respectively) (P<0,001). The prevalence of thyroid nodule was significantly higher in DM group than the prediabetic and the control groups, in the prediabetic group than the control group (61,0%, 44,4%, and 17,2%, respectively, P<0,001). Among patients with nodular goiters, the evaluation according to the mean of maximum nodule diameter revealed significantly lower values in the control group (mean value: 8,1±3,8 mm) than the other two groups (P<0,001). The mean values were higher in DM group than the prediabetics, though not significantly (12,2±7,7 and 11,2±7,2 mm, respectively). The results demonstrate that patients with DM and prediabetes have significantly increased thyroid volume and nodule prevalence according to the control group. Our findings are probably the first evidence showing prospectively morphological and functional alterations in the thyroid gland caused by a pathological course of disturbed glucose metabolism in which insulin resistance plays a basic role.