Measures of Thyroid Function among Belarusian Children and Adolescents Exposed to Iodine-131 from the Accident at the Chernobyl Nuclear Plant

Abstract

Background: Thyroid dysfunction after exposure to low or moderate doses of radioactive iodine-131 (131I) at a young age is a public health concern. However, quantitative data are sparse concerning 131I-related risk of these common diseases.Objective: Our goal was to assess the prevalence of thyroid dysfunction in association with 131I exposure during childhood (≤ 18 years) due to fallout from the Chernobyl accident.Methods: We conducted a cross-sectional analysis of hypothyroidism, hyperthyroidism, autoimmune thyroiditis (AIT), serum concentrations of thyroid-stimulating hormone (TSH), and autoantibodies to thyroperoxidase (ATPO) in relation to measurement-based 131I dose estimates in a Belarusian cohort of 10,827 individuals screened for various thyroid diseases.Results: Mean age at exposure (± SD) was 8.2 ± 5.0 years. Mean (median) estimated 131I thyroid dose was 0.54 (0.23) Gy (range, 0.001–26.6 Gy). We found significant positive associations of 131I dose with hypothyroidism (mainly subclinical and antibody-negative) and serum TSH concentration. The excess odds ratio per 1 Gy for hypothyroidism was 0.34 (95% CI: 0.15, 0.62) and varied significantly by age at exposure and at examination, presence of goiter, and urban/rural residency. We found no evidence of positive associations with antibody-positive hypothyroidism, hyperthyroidism, AIT, or elevated ATPO.Conclusions: The association between 131I dose and hypothyroidism in the Belarusian cohort is consistent with that previously reported for a Ukrainian cohort and strengthens evidence of the effect of environmental 131I exposure during childhood on hypothyroidism, but not other thyroid outcomes.

Morphological and functional changes in neonatally X-irradiated thyroid gland in rats

“…Contrasting with the evident correlation between childhood radiation exposure and an increase in thyroid cancer incidence, the effects of radiation on thyroid status are less clear. Belarusian and Ukrainian cohort studies suggested that an increase in serum TSH levels was related to childhood exposure to 131 I [8,9], while other studies did not suggest any relationship [10,11]. In rodent models, an early study demonstrated that whole body or cervical X-irradiation could change serum thyroid hormone levels in adult rats [12].…”

Reliability of Questionnaire Data in the Distant Past

“…We examined the reliability of responses to questions about residential history and dietary pattern in the distant past obtained for a cohort of 11,732 subjects of a long-term epidemiological study of thyroid cancer and other thyroid disease in individuals exposed in childhood and adolescence to radiation following the Chernobyl accident, which occurred on 26 April 1986 (Stezhko et al 2004; Zablotska et al 2011; Ostroumova et al 2013). The majority of the study subjects or his/her relatives were interviewed at least two times between 1996 and 2007 during two medical screenings of the cohort.…”

Thyroid Dose Estimates for a Cohort of Belarusian Children Exposed to131I from the Chernobyl Accident: Assessment of Uncertainties

“…The U.S. National Cancer Institute, in collaboration with the Belarusian Ministry of Health, has been conducting a study of thyroid cancer and other thyroid diseases in a cohort of 11,732 persons who were exposed in childhood and adolescence to fallout from the Chernobyl accident that occurred on April 26, 1986 (10–12). To evaluate the radiation risk of thyroid diseases, deterministic thyroid doses were reconstructed for the study subjects based on estimated 131 I activity in the thyroid derived from direct thyroid measurements of each cohort member and responses to interviews of all subjects on residential history, consumption of milk, milk products and leafy vegetables and administration of stable iodine (13).…”