Background. The present multicenter study was designed for a retrospective assessment of the clinical course, therapy and co-morbidity of autoimmune thyroiditis in childhood and adolescence.

Patients and methods. 130 patients (108 female, 22 male) with a mean age of 11.1±3.3 years were evaluated on the basis of patient charts using standardized questionnaires.

Results. In the total group of 130 patients 70, 55, and 13 periods of euthyroidism, hypothyroidism and hyperthyroidism, respectively, were observed. Treatment of euthyroid autoimmune thyroiditis with L-thyroxine was of no benefit with regard to a reduction in thyroid gland volume as evaluated by ultrasound examination. 20% of patients suffered from substantial co-morbidity, among which diabetes mellitus type 1 was the commonest.

Conclusions. The present study suggests no advantage to the treatment of euthyroid autoimmune thyroiditis with L-thyroxine. Special attention should be paid to the early detection of co-morbidity associated with autoimmune thyroiditis of childhood and adolescence.