Autoimmune Thyroid Disorders in Patients with Type 1 Diabetes Mellitus; Results of Long Term Follow up of a Large Cohort of Patients in Endocrine and Diabetes Clinics of Tabriz University of Medical Sciences

Missing the diagnosis of thyroid dysfunction in type 1 diabetes mellitus (DM) may have many deleterious consequences. Screening of these patients for thyroid abnormalities at initial diagnosis of type I DM may identify only a small proportion of affected subjects. The aim of this study was to determine thyroid functional status, the prevalence of thyroid autoimmunity, their natural history and the results of long term follow up of a large cohort of population with type 1 DM. A total of 386 type 1 diabetic patients with no known thyroid dysfunction prior to diagnosis of diabetes were enrolled into the study and followed up from 1 to 17 years. (9.8±4 years) Clinical examination was performed and serum TSH and thyroperoxidase antibodies titer were measured at first presentation and repeated at regular intervals. Among 386 studied patients with type 1 DM, aged 15.6±7.7 years, sixty three (16.3%) patients developed thyroid dysfunction during the follow up period; fifty three (13.8%) subjects with hypothyroidism, 9 patients (2.3%) with hyperthyroidism, and 2 patients with postpartum thyroiditis. In this longitudinal study, 115 (30%) patients had high titers of TPO antibodies in their sera. Using Caplan-Meier curve, 50% of subjects developed thyroid abnormalities during the first 10 years after diagnosis of type 1 DM. The results of this study showed that thyroid dysfunction was more prevalent in type 1 diabetic patients. A large proportion of individuals developed thyroid dysfunction during the long term follow up.