The prevalence of anti-thyroid peroxidase antibodies and autoimmune thyroiditis in children and adolescents in an iodine replete area

Background: The iodine supply of the population in Berlin has normalized during the last 5 years. Therefore autoimmune thyroiditis has become the most important differential diagnosis in children and adolescents with goiter. Objective: The aim of the present study was to define the prevalence of anti-thyroid peroxidase (TPO) antibodies and autoimmune thyroiditis in children and adolescents with a normalized iodine intake. Design: To enable the measurement of antibodies to thyroid peroxidase (anti-TPO-Ab) in a large cohort, a method to determine anti-TPO-Ab in dried filter paper blood spots was established. In co-operation with pediatricians the antibody prevalence was assessed and data regarding thyroid size, echostructure and the medical history concerning iodine intake and familial thyroid diseases were collected. Methods: 660 children and adolescents participated in the study; urinary iodine, TSH and TPO-Ab were measured and an ultrasound of the thyroid gland was performed. Results: The sensitivity of the newly established filter paper assay was 91.8% and specificity was 100%. The results confirmed the improved iodine supply, with a median urinary iodine concentration of 139 mug iodine/g creatinine. The prevalence of anti-TPO-Ab was 3.4% with a female to male ratio of 2.7:1. Conclusion: The prevalence of anti-TPO-Ab is lower or equal to data reported from other iodine sufficient areas. Data from a moderate iodine deficiency in schoolchildren range from 0.0 to 7.3%. Using the new filter paper method field studies can be implemented to monitor the effect of changes in iodine nutrition on thyroid autoimmunity. Furthermore, this study on the prevalence of anti-TPO-Ab in a cohort of healthy children and adolescents in an iodine replete area can serve as reference data for future investigations and for the comparison with other groups of patients with increased risks for thyroid autoimmunity.