Prevalence of thyroid dysfunction among patients with type 2 diabetes mellitus

Introduction: Studies shown that prevalence of thyroid disease is 2-3 times higher in Type 1 DM population compared to non-diabetic population. The prevalence of thyroid disease among Type 2 DM population is not well known. In present study, we aimed to investigate the prevalance of thyroid dysfunction in diabetic patients and the effect of thyroid hormone levels on metabolic control and diabetic complications. Materials and Methods: A retrospective analysis of 2164 patients were done who were treated at Istanbul Faculty of Medicine, Department of Endocrinology and Diabetes between January 2017 and January 2020. 1441 parients have been excluded from the study due to not meeting the inclusion criteria. 723 patients who had Type 2 DM diagnosis who met the criteria were included. Clinical, laboratory and thyroid functions of those patients were evaluated. Results: 377 (52.1%) of patients were male, 346 (47.9%) of patients were female. The mean age was 58.3±11.2 and it was similar between women (59.4 ± 12.1) and men (57.3 ± 11.8). The mean TSH was detected as 2.6 mIU/L, mean sT4 was 16.4 pmol/L and mean sT3 was 4.6 pmol/L. The frequency of thyroid dysfunction was detected to be %21.4 and the female/male ratio was found to be 3 times against women (p=0.001). Clinical condition was evaluated according to thyroid function tests; 78.6% of patients were euthyroid, %15.1 were hypothyroid, %2 were hyperthyroid and 4.3% were subclinically thyroid dysfunction. Free T3 concentration was sigbnificantly lower in patients with diabetic nephropathy, diabetic retinopathy, hypertension and peripheric artey disease. Patients with diabetic nephropathy had higher TSH and lower free T3 concentrations than the patients without nephropathy. Conclusion: In our study, the frequency of thyroid dysfunction among Type 2 DM population was approximately 3 times higher than compared to the healthy population. Therefore, we suggest regular follow-up of thyroid function tests among Type2 DM patients. Key words: Type 2 diabetes mellitus, thyroid dysfunction, TSH