CLINICAL STUDY A prospective study of thyroid function, morphology and autoimmunity in young patients with type 1 diabetes

Objective: Thyroid autoantibodies (TA) and thyroid ultrasonography are widely used in the diagnosis of autoimmune thyroid disease (AITD). However, we know little of the significance of having ultraso-nographic abnormalities (USabn) without having any other signs of AITD. In a previous population-based study of 105 young patients with type 1 diabetes (T1DM) we found a high prevalence (42%) of USabn. In the present study we evaluate the development of both USabn and TA in a 3-year follow-up of this cohort. Design: Of the 105 previously investigated children and adolescents with T1DM (aged 5–21 years), 101 were re-examined. Serum concentrations of tri-iodothyronine (T3), thyroxine (T4), TSH, thyroid peroxidase antibodies (TPOab) and thyroglobulin antibodies (Tgab), as well as thyroid size and mor-phology were determined in all patients. Results: During the 3 years follow-up period, the prevalence of thyroid dysfunction increased from 5 to 8%, the prevalence of TPOab was unchanged at 13%, while the prevalence of Tgab decreased from 14 to 7%. The prevalence of USabn increased from 42 to 49%. Most patients presented USabn at both examinations. Patients with USabn had a higher prevalence of TA than those without USabn ðP 0:038Þ and higher serum levels of TSH ðP 0:027Þ: All patients with thyroid dysfunc-tion presented with USabn. However, many patients with USabn had no other signs of AITD. Conclusions: A high prevalence of thyroid dysfunction, TA and thyroid USabn were found in young patients with T1DM. Thyroid USabn was a sensitive but non-specific marker of AITD and is therefore unsuitable for screening purposes. Instead, we recommend regular screening using serum TSH in the follow-up of young diabetic patients. European Journal of Endocrinology 148 245–25