Increasing incidence of childhood thyrotoxicosis in a population-based area of central Sweden

Aim: To study the incidence, prevalence and clinical characteristics of childhood thyrotoxicosis in a population‐based area comprising five counties in central Sweden. Methods: Retrospective analysis of the medical records of all children below 16 y of age with thyrotoxicosis during a 10‐y study period. Results: Forty‐six children were identified with thyrotoxicosis. The median age at onset was 11.7 y and 85% were females. At the end of the study period on 31 December 1999, the prevalence was 0.08 per 1000. The mean annual incidence was four times higher in the second 5‐y period than in the first (2.7 and 0.7 per 100000, respectively; p < 0.001). A first‐degree relative with thyrotoxicosis was found in 21% of the children and 11/46 children (24%) showed autoimmune‐related co‐morbidity. Increased heart rate was observed in 95%, goitre in 67% and exophthalmos in 33% of the children. TSH was completely suppressed and free T4 was clearly above the upper reference limit in all children. TSH receptor‐stimulating antibodies and peroxidase antibodies were observed in 80% and 71% of the children, respectively. Conclusion: This study indicates an increase in the incidence of childhood thyrotoxicosis in a population‐based area of central Sweden. A prospective study aimed at identifying specific aetiological risk factors for development of thyrotoxicosis has been initiated.