Thyroid autoimmunity and the subsequent development of islet and celiac autoimmunity in the TEDDY study

We aimed to determine if thyroid autoimmunity is associated with a child’s risk for subsequent development of islet or celiac autoantibodies. Children at high genetic risk of type 1 diabetes were followed for thyroid autoimmunity (thyroid peroxidase antibodies [TPOAb] and thyroglobulin antibodies [TGAb]), islet autoimmunity (IA), and celiac disease autoimmunity [CDA] in The Environmental Determinants of Diabetes in the Young (TEDDY) study. Out of 5482 children tested for thyroid autoimmunity, IA, and CDA, 39% developed at least one autoantibody. At age 14 years, thyroid autoimmunity co-occurred with IA in 59 children (15 more cases than expected by chance alone, p = 0.02), and with CDA in 125 children (26 cases above expected, p = 0.01). The risk of developing IA or CDA after thyroid autoimmunity varied by which thyroid autoantibody appeared first: TPOAb-first was associated with both IA (HR 1.92, 95% CI 1.09, 3.40) and CDA (1.69, 95% CI 1.03, 2.76), whereas TGAb-first was not associated with the risk of either. IA and CDA are frequently found in connection to thyroid autoimmunity in children and young adolescents. The relationships of thyroid autoimmunity with IA and CDA depend on which thyroid autoantibody appears first.