Background: Autoimmune thyroid disease (AITD) represents the most frequent associated manifestation of the autoimmune disease in children with Type 1 diabetes mellitus (T1DM). The aim of the study was to evaluate the prevalence and natural course of AITD in unselected cohort of diabetic children.
Methods and results: TSH, free thyroxin, thyreoglobulin autoantibodies (Ab-hTG), peroxidase autoantibodies (Ab-TPO) and thyroid sonography were prospectively evaluated (1 to 6 years; 323 patient-years) in 110 patients with T1DM (age 2.1-20.8 years; 60 boys). Mild elevation of Ab-hTG and/or Ab-TPO levels (> 100, < 1000 mIU/l) was found in 19 patients (17%; boys:girls 1:2.2). Out of these, only 2 had increased thyroid volume and/or abnormal echotexture. In 9 of these patients, levels of autoantibodies subsequently declined below 100 mIU/l, remained unchanged in 9 patients and only in one case increased over 1000 mIU/l ("benign form" of AITD). All patients remained euthyroid. Severe elevation of Ab-hTG and/or Ab-TPO (> 1000 mIU/l) was found in 12 patients (11%; boys:girls 1:1). Out of these, eight had increased thyroid volume and ten had abnormal echotexture. Subclinical hypothyroidism developed within the observation period in nine of them (boys:girls 2:1).
Conclusions: AITD was found in 31 (28%) children and adolescents with T1DM. Whereas mild elevation of Ab-hTG and/or Ab-TPO levels was not accompanied with morphological changes of the thyroid and did not predict functional disorder, severely elevated levels were associated with the early risk of subclinical hypothyroidism.