Background: Type 1 diabetes mellitus (T₁DM) as an autoimmune disorder is associated with other autoimmune diseases such as autoimmune thyroid (AIT) disease. The aim of this study was to determine the prevalence of AIT in children who were referred to Amirkola Endocrine Clinic (north of Iran).

Methods: This cross-sectional study was carried out on 100 diabetic children aged 1-15 years during 2008-2013, who were referred to the pediatric endocrine clinic. Serum levels of anti-thyroid peroxidase (Anti-TPO) and anti-thyroglobulin (anti-Tg) antibodies and Thyrotropin Stimulating Hormone (TSH) were measured by Immune Chemiluminescence assay, and demographic information was obtained from patients'medical records. The collected data were analyzed using SPSS 18.

Results: AIT was found in 13% of patients (8% female and 5% male). Significant levels were found for Anti-TPO (3%), anti-Tg (2%), and both antibodies (8%) in patients with AIT. Thyroid dysfunction was observed in 8 of 13 patients with AIT versus 2 of 87 patients without AIT (P<0.001). AIT was seen in 9% of diabetic children who had diabetes for less than one year versus 4% of the rest of diabetic children with duration more than one year (p<0 .0001).

Conclusion: Because the majority of diabetic children with significant titers of antibodies developed thyroid disease, so thyroid function tests are necessary to reduce the risk of undiagnosed hypothyroidism in these patients.