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Correspondence Volume 122 | Issue 02 | February 2014

Environ Health Perspect; DOI:10.1289/ehp.1307737R

Iodine-131 and Thyroid Function: Ostroumova et al. Respond

Evgenia Ostroumova,1 Alexander Rozhko,2 Maureen Hatch,1 Kyoji Furukawa,3 Olga Polyanskaya,2 Robert J. McConnell,4 Eldar Nadyrov,2 Sergey Petrenko,5 George Romanov,2 Vasilina Yauseyenka,2 Vladimir Drozdovitch,1 Viktor Minenko,6 Alexander Prokopovich,2 Irina Savasteeva,2 Lydia B. Zablotska,7 Kiyohiko Mabuchi,1 and Alina V. Brenner1

1Division of Cancer Epidemiology and Genetics, National Cancer Institute, National Institutes of Health, Department of Health and Human Services, Bethesda, Maryland, USA; 2The Republican Research Center for Radiation Medicine and Human Ecology, Gomel, Belarus; 3Department of Statistics, Radiation Effects Research Foundation, Hiroshima, Japan; 4The Thyroid Center, Columbia University, New York, New York, USA; 5Department of Anthropoecology and Epidemiology, International Sakharov Environmental University, Minsk, Belarus; 6Belarusian Medical Academy of Post-Graduate Education, Minsk, Belarus; 7Department of Epidemiology and Biostatistics, University of California, San Francisco, San Francisco, California, USA

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Citation: Ostroumova E, Rozhko A, Hatch M, Furukawa K, Polyanskaya O, McConnell RJ, Nadyrov E, Petrenko S, Romanov G, Yauseyenka V, Drozdovitch V, Minenko V, Prokopovich A, Savasteeva I, Zablotska LB, Mabuchi K, Brenner AV. 2014. Iodine-131 and Thyroid Function: Ostroumova et al. Respond. Environ Health Perspect 122:A40–A41; http://dx.doi.org/10.1289/ehp.1307737R

E-mail: ostroume@mail.nih.gov

The authors declare that they have no actual or potential competing financial interests.

Published: 1 February 2014

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Sun’s comments about the relationship between iodine-131 (131I), hypothyroidism, and simple diffuse goiter suggest a misunderstanding of our study findings. We reported a significantly higher—rather than lower—radiation-associated risk of hypothyroidism among study participants without goiter than in the participants with goiter (Ostroumova et al. 2013). Specifically, the excess odds ratio (EOR) per Gray of 131I thyroid dose was 0.50 [95% confidence interval (CI): 0.24, 0.90] in participants without goiter and 0.04 (95% CI: –0.09, 0.32) in those with goiter. We also reported a lack of significant variation of EOR per Gray for hypothyroidism by levels of urinary iodine (p = 0.23), although in the discussion we noted that iodine concentration in spot urine samples, unlike presence of diffuse goiter, reflects current levels of iodine intake and is subject to high within-individual variability.

The territories of Belarus were known to be iodine deficient before the Chernobyl accident; in the Soviet Union there was a system of iodine prophylaxis that was discontinued by the mid-1980s (Kholodova and Fedorova 1992). In 1995–1998, five of the six Belarus regions were classified as having moderate iodine deficiency, whereas the Gomel region, most heavily contaminated with 131I, was classified as having mild iodine deficiency partly due to some iodine supplementation in this area after the Chernobyl accident (Arinchin et al. 2000). High prevalence of diffuse goiter detected by ultrasound in children and adolescents in the relatively uncontaminated Brest region (27.8%) and low prevalence in the heavily contaminated Gomel region (5.6%) (Arinchin et al. 2000) support the idea that these differences are attributed to different intake of dietary iodine and not to 131I exposure. Moreover, there is little evidence of a dose–response association between thyroid exposure and simple diffuse goiter in other radiation-exposed cohorts (Ron and Brenner 2010).

As we described in the “Materials and Methods” of our article (Ostroumova et al. 2013), availability of individual direct measurements of thyroid radioactivity served as a key criterion for inclusion into the study. All study participants had direct measurements of thyroid radioactivity performed within 2 months after the accident. In the methods for dosimetry, we cited the article by Drozdovitch et al. (2013), in which dose reconstruction methods were described in detail. We also noted that intake of 131I on average accounted for about 95% of the estimated thyroid dose, whereas the contribution of other short-lived radioiodines, external exposures, and internal exposure from cesium-137 and cesium-134 was minor (Bouville et al. 2007).

We appreciate Sun’s interest in our study and hope our response is useful.


References

Arinchin A, Gembicki M, Moschik K, Skalyzhenko A, Khmara I, Korytko N, et al. 2000. Goiter prevalence and urinary iodine excretion in Belarus children born before and after the Chernobyl accident. IDD Newsletter 16(1). Available: http://iccidd.server295.com/media/IDD%20​Newsletter/1991-2006/feb2000.htm#a3 [accessed 9 January 2014].

Bouville A, Likhtarev IA, Kovgan LN, Minenko VF, Shinkarev SM, Drozdovitch VV. 2007. Radiation dosimetry for highly contaminated Belarusian, Russian and Ukrainian populations, and for less contaminated populations in Europe. Health Phys 93(5):487–501.

Drozdovitch V, Minenko V, Khrouch V, Leshcheva S, Gavrilin Y, Khrutchinsky A, et al. 2013. Thyroid dose estimates for a cohort of Belarusian children exposed to radiation from the Chernobyl accident. Radiat Res 179(5):597–609.

Kholodova EA, Fedorova LP. 1992. Prevalence of endemic goiter in Byelarus [in Russian]. Probl Endokrinol (Mosk) 38(6):30–31.

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.

Ron E, Brenner A. 2010. Non-malignant thyroid diseases after a wide range of radiation exposures. Radiat Res 174(6):877–888.


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