Analysis of thyroid autoantibodies and the risk of insulin depletion after the clinical onset of acute-onset type 1 diabetes in Japanese patients: the TIDE-J study

Introduction: Type 1 diabetes is often accompanied by autoimmune thyroid disease. We aimed to investigate the clinical characteristics of Japanese patients with acute-onset type 1 diabetes and thyroid autoantibodies, focusing on decreased endogenous insulin secretion. Materials and methods: We examined 80 patients with acute-onset type 1 diabetes, classifying them into two groups with and without thyroid autoantibodies and compared the clinical characteristics of the two groups. A fasting serum C-peptide immunoreactivity (CPR) of less than 0.1 ng/mL was defined as insulin depletion. Results: In patients with thyroid autoantibodies, the median fasting serum CPR levels at the fourth year after the onset of type 1 diabetes were significantly lower than in those without thyroid autoantibodies (p = 0.02). The cumulative incidence of insulin depletion at 5 years of duration after diagnosis of type 1 diabetes was significantly higher in thyroid autoantibody-positive group than in thyroid autoantibody-negative group (p = 0.01). In the Cox proportional models adjusted for selected baseline factors (age, sex, and BMI), the presence of thyroid autoantibodies did not increase the risk of insulin depletion within 5 years after the onset. However, in bivariate Cox proportional hazards models that investigated the association between thyroid autoantibodies and each baseline factor, the presence of thyroid autoantibodies significantly increased the risk of insulin depletion. Conclusions: Our study showed that Japanese patients with acute-onset type 1 diabetes and positive for thyroid autoantibodies had a higher risk of insulin deficiency within 5 years after the onset than those without thyroid autoantibodies.