Thyroid autoantibodies and thyroid function in subjects exposed to Chernobyl fallout during childhood: evidence for a transient radiation-induced elevation of serum thyroid antibodies without an increase in thyroid autoimmune disease.

CONTEXT: An increase in the prevalence of thyroid autoantibodies (ATAs) was reported 6-8 yr after the Chernobyl accident in radiation-exposed children and adolescents.

OBJECTIVE: Our objective was to reassess the effects of childhood radiation exposure on ATAs and thyroid function 13-15 yr after the accident.

DESIGN AND SETTING: We measured the antithyroglobulin (TgAbs) and antithyroperoxidase (TPOAbs) antibodies and TSH in 1433 sera collected between 1999 and 2001 from 13- to 17-yr-old adolescents born between January 1982 and October 1986 in paired contaminated and noncontaminated villages of Belarus, Ukraine, and Russia. A total of 1441 sera was collected from age- and sex-matched controls living in Denmark and Sardinia (Italy). Free T(4) and free T(3) were measured when TSH was abnormal.

RESULTS: TPOAb prevalence was higher in contaminated than in noncontaminated Belarusian children (6.4 vs. 2.4%; P = 0.02) but lower than previously reported (11%) in a different contaminated Belarus village. No difference in TPOAb prevalence was found in Ukrainian and Russian villages. TgAbs showed no difference between contaminated and noncontaminated Belarus and Ukraine, whereas in Russia they showed a relative increase in the exposed subjects with respect to the unexposed, who showed an unexpectedly lower prevalence of TgAbs. Besides radiation exposure, female gender was the only variable significantly correlated with ATAs in all groups. ATA prevalence in nonexposed villages of Belarus, Ukraine, and Russian Federation did not differ from that found in Sardinia and Denmark. With few exceptions, thyroid function was normal in all study groups.

CONCLUSIONS: TPOAb prevalence in adolescents exposed to radioactive fallout was still increased in Belarus 13-15 yr after the Chernobyl accident. This increase was less evident than previously reported and was not accompanied by thyroid dysfunction. Our data suggest that radioactive fallout elicited a transient autoimmune reaction, without triggering full-blown thyroid autoimmune disease. Longer observation periods are needed to exclude later effects.