PREVALENCE OF THYROID AUTOANTIBODIES IN CHILDREN AND ADOLESCENTS FROMBYELARUS EXPOSED TO THE CHERNOBYL RADIOACTIVE FALLOUT

Background The long-term effects of ionising radiation, including radi oiodine, on thyroid function are not well known. We compared thyroid i mmunity and function in two groups of children from Belarus, one of wh om was exposed to the radioactive fallout of Chernobyl. Methods We mea sured serum free thyroxine 4 (free T4), free T3, and thyrotropin hormo ne (TSH) and the prevalence of thyroid autoantibodies (antithyroglobul in and antithyroperoxidase), in 287 children or adolescents living in Hoiniki (average caesium contamination of 5.4 Ci/km(2)). We also studi ed 208 children and adolescents living in Braslav (average contaminati on <0.1 Ci/km(2)), who were age 12 years or less at the time of the Ch ernobyl accident. Findings The prevalence of antithyroglobulin or anti thyroperoxidase, or both, was significantly higher (p=0.0001) in indiv iduals living in Hoiniki (56 [19.5%] of 287) than in those living in B raslav (eight [3.8%] of 208). In both villages, no sex differences wer e found in the antibody prevalence before age 13 years. Thereafter, a significantly higher prevalence of thyroid autoantibodies was found in girls from Hoiniki. The increase in the prevalence of circulating ant ibodies in the contaminated group was already apparent in individuals who, at the time of the accident, were in utero or newborn (15.7%), an d was even more pronounced in children of 9 years or more (35.1%). No major alterations of serum FT-4, FT-3, or TSH were found. Interpretati on 6-8 years after the Chernobyl accident, a significant increase in t hyroid autoimmunity was found in children exposed to radioactive fallo ut. Pubertal age in girls is a risk factor for increased prevalence of thyroid autoimmunity. The autoimmune phenomena are limited to an incr eased prevalence of circulating thyroid autoantibodies without evidenc e of significant thyroid dysfunction, The future development of clinic ally relevant thyroid autoimmune diseases, especially hypothyroidism, is a possibility.