Abstract
PurposeStable iodine prophylaxis helps prevent childhood thyroid cancer in nuclear emergencies; however, there is limited information on its effect on thyroid function. This study aimed to examine thyroid function and autoimmunity among children and adolescents that took stable iodine after the Fukushima Nuclear Disaster.MethodsFor this observational study, data were obtained from children and adolescents that underwent thyroid cancer screening at Hirata Central Hospital from April 2012 to March 2018. Participant characteristics, including possible hypothyroidism and hyperthyroidism, were compared between the prophylaxis and no-prophylaxis groups. Multivariable logistic regression models were used to assess for possible hypothyroidism, autoantibodies positive, and hyperthyroidism.ResultsA total of 1,225 participants with stable iodine prophylaxis and 3,946 without prophylaxis were enrolled. Of those participants, blood samples were available for 144 and 1,201 participants in the prophylaxis and no-prophylaxis groups, respectively. There were 17 (11.8%) and 146 cases (12.2%) of possible hypothyroidism or autoantibodies positive cases in the prophylaxis and no-prophylaxis groups, respectively, and there were no cases and 3 cases (0.2%) of possible hyperthyroidism in those two groups, respectively. Multivariable analysis for possible hypothyroidism revealed no association between stable iodine intake and possible hypothyroidism or autoantibodies positive [odds ratio 0.716 (95% confidence interval 0.399–1.284)] (p = 0.262). We did not perform multivariable analysis for hyperthyroidism due to the limited number of cases.ConclusionSignificant adverse effects of stable iodine intake on thyroid function were not observed among children and adolescents 7 years after the Fukushima Nuclear Disaster.
Highlights
Stable iodine prophylaxis is important for preventing thyroid cancer in nuclear emergencies along with other strategies such as evacuation, sheltering, and restricting the consumption of contaminated materials [1, 2]
It was reported that serum T3 and T4 levels and antibodies in these children showed no significant differences between the prophylaxis and noprophylaxis groups in Poland after the Chernobyl accident [8, 10]
The analysis revealed that age at the time of the disaster, years since the disaster, male sex, school screening, and family history of thyroid diseases were factors significantly associated with possible hypothyroidism (p < 0.05)
Summary
Stable iodine prophylaxis is important for preventing thyroid cancer in nuclear emergencies along with other strategies such as evacuation, sheltering, and restricting the consumption of contaminated materials [1, 2]. Exhaustive distribution, timely and specific instructions for intake, and provision of pharmacological information should be addressed in order to adequately implement stable iodine intake for children and adolescents [4] Even though it is a key strategy in cases of nuclear emergencies, reported adverse effects of stable iodine intake include allergies, skin rashes, swelling of salivary glands, and thyroid dysfunction among other effects [5,6,7,8]. Hypothyroidism can occur in fetuses after maternal iodine overload or in newborns during breastfeeding These possible side effects during the neonatal period are concerning if not diagnosed and treated by hormonal therapy, as they may impair the longterm neurological and mental development of the child [9]. Besides the Polish study, there is limited information on thyroid hormone levels amongst children and adolescents that took stable iodine in actual disaster cases
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