Prevalence of thyroid dysfunction and antithyroid antibodies in type 1 diabetic mellitus patients and their first degree relatives

Diabetes Mellius Type 1 (DM1) is frequently associated to Autoimmune Thyroid Disease (AITD). The prevalence of AITD among diabetic patients varies between 3 to 50% and the incidence is also big among their family members, when compared to the population in general. Objectives: To investigate the prevalence of AITD in patients with DM1; to evaluate possible differences concerning the clinical-evolutive behavior of DM1 among diabetic patients with or without AITD and to study the prevalence of AITD among the diabetes patients' relatives. Materials and Methods: 124 prontuaries of diabetic patients (type 1) were revised and data was gathered concerning the thyroid function and the anti-thyroid antibodies. Patients with and without AITD were compared in relation to the level of glycosylated hemoglobin, the presence of acute and chronic complications, the age of the patient at the time of the diagnosis, time of evolution of the disease, daily dose of insulin and other factors. A control case study was conducted with 54 first degree relatives of the diabetic patients who took part in the study; the thyroid function as well as the presence of anti-thyroid antibodies were evaluated in 32 of those first degree relatives with AITD, and in 22 of those without AITD. Results: The prevalence of AITD and of hormonal dysfunction among diabetic patients was 35.5% and 19.3%, respectively. No significant differences were found between groups in respect to clinical outcome or to diabetic chronic complications. However, prevalence of AITD and hormonal dysfunction were found to be higher among first degree relatives of diabetic patients with AITD than among relatives of diabetic patients without AITD. Conclusions: The prevalence of autoimmune thyroid disease in diabetic patients and in their first degree relatives is high. Thyroid function screening is therefore justified in these cases, especially in first degree relatives of diabetics with autoimmune thyroid disease.