Correspondence Volume 122 | Issue 2 | February 2014
Environ Health Perspect; DOI:10.1289/ehp.1307737
Iodine-131 and Thyroid Function
Global Health and Environmental Sciences, Tulane University School of Public Health and Tropical Medicine, New Orleans, Louisiana, USA
Ostroumova et al. (2013) reported an association between iodine-131 (131I) dose and hypothyroidism in the Belarusian cohort, a cohort of individuals exposed to 131I from fallout of the Chernobyl accident when they were ≤ 18 years of age. Ostroumova et al. also examined other thyroid outcomes: hyperthyroidism, autoimmune thyroiditis, serum concentrations of thyroid-stimulating hormone, and autoantibodies to thyroperoxidase.
It may not be appropriate to include participants with other thyroid outcomes in the analysis because those thyroid outcomes could be indirectly associated with exposure. Chernobyl is in an iodine-deficient area (Ishigaki et al. 2001), and the prevalence of goiters among children ≤ 18 years of age has been reported at > 15% in this area (Hatch et al. 2011). Is high prevalence of goiters in the area caused by normal iodine deficiency or by the 131I? If the goiters were caused by 131I, the relationship between the 131I and hypothyroidism is still unclear, even though Ostroumova et al. (2013) stratified the data according to the presence of goiters. Hypothyroidism can also cause goiters (Wilkins et al. 1954); thus, goiter is just a serious hypothyroidism. That could be the explanation for the higher excess odds ratio in the group with goiter compared with the group without goiter shown in Table 3 of Ostroumova et al. (2013). It would have been better for Ostroumova et al. to perform a stratified analysis on the relationship between 131I and hypothyroidism based on the normal iodine level of the individual rather than the presence of goiter.
Ostroumova et al. (2013) also claimed that the thyroid radioactivity of individuals from the Belarus cohort was based on a previous study (Stezhko et al. 2004). However, Stezhko et al. (2004) did not provide the details of the individual radioactive iodine measurement. Were the original radioactive iodine measurements generated from a formula or modeled based on food intake or soil contamination, or was the 131I exposure level actually measured for each individual? The answer to this question is necessary because the two methods have different credibility. In addition, the exposure described by Stezhko et al. (2004) included 131I as well as other radioactive isotopes of iodine, not 131I alone. I would like to know whether Ostroumova et al. (2013) separated 131I from other radioactive iodine isotopes. Cesium-137 should also be considered as a potential confounder in the relationship between 131I and hypothyroidism.
Hatch M, Polyanskaya O, McConnell R, Gong Z, Drozdovitch V, Rozhko A, et al. 2011. Urinary iodine and goiter prevalence in Belarus: experience of the Belarus–American cohort study of thyroid cancer and other thyroid diseases following the Chornobyl nuclear accident. Thyroid 21:429–437.
Ostroumova E, Rozhko A, Hatch M, Furukawa K, Polyanskaya O, McConnell RJ, et al. 2013. Measures of thyroid function among Belarusian children and adolescents exposed to iodine-131 from the accident at the Chernobyl nuclear plant. Environ Health Perspect 121:865–871; doi: 10.1289/ehp.1205783.
Stezhko VA, Buglova EE, Danilova LI, Drozd VM, Krysenko NA, Lesnikova NR, et al. 2004. A cohort study of thyroid cancer and other thyroid diseases after the Chornobyl accident: objectives, design and methods. Radiat Res 161:481–492.
Wilkins L, Clayton GW, Berthrong M. 1954. Development of goiters in cretins without iodine deficiency: hypothyroidism due to apparent inability of the thyroid gland to synthesize hormone. Pediatrics 13:235–246.
ISEE 2015 Abstracts Now AvailableEHP is pleased to present the abstracts for the 2015 annual conference of the International Society for Environmental Epidemiology (ISEE), “Addressing Environmental Health Inequalities,” held 30 August–3 September 2015 in São Paulo, Brazil.
New Editor-in-ChiefWe are pleased to announce that Sally Perreault Darney has been selected as the new Editor-in-Chief of EHP. Sally comes to EHP from the U.S. Environmental Protection Agency, where she most recently co-led a large research project focused on assessing health disparities in vulnerable groups and providing healthy environments for children. Learn more about Sally and her vision for the journal in the September issue of EHP.
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