Autoimmune thyroiditis and exposure to iodine 131 in the Ukrainian cohort study of thyroid cancer and other thyroid diseases after the Chornobyl accident: results from the first screening cycle (1998-2000).

CONTEXT: Due to the Chornobyl accident, millions were exposed to radioactive isotopes of iodine and some received appreciable iodine 131 (131I) doses. A subsequent increase in thyroid cancer has been largely attributed to this exposure, but evidence concerning autoimmune thyroiditis (AIT) remains inconclusive. OBJECTIVE: The objective of the study was to quantify risk of AIT after 131I exposure. DESIGN/SETTING/PARTICIPANTS: Baseline data were collected from the first screening cycle (1998-2000) of a large cohort of radiation-exposed individuals (n = 12,240), residents of contaminated, iodine-deficient territories of Ukraine. Study individuals were under the age of 18 yr on April 26, 1986, and had thyroid radioactivity measurements made shortly after the accident. OUTCOMES: AIT was defined a priori based on various combinations of elevated antibodies to thyroid peroxidase (ATPO), TSH, and clinical findings; elevated ATPO were considered to be an indicator of thyroid autoimmunity. RESULTS: No significant association was found between 131I thyroid dose estimates and AIT, but prevalence of elevated ATPO demonstrated a modest, significant association with 131I that was well described by several concave models. This relationship was apparent in individuals with moderately elevated ATPO and euthyroid, thyroid disease-free individuals. CONCLUSIONS: Twelve to 14 yr after the Chornobyl accident, no radiation-related increase in prevalence of AIT was found in a large cohort study, the first in which 131I thyroid doses were estimated using individual radioactivity measurements. However, a dose-response relationship with ATPO prevalence raises the possibility that clinically important changes may occur over time. Thus, further follow-up and analysis of prospective data in this cohort are necessary.

Thyroid carcinoma in children and adolescents in Ukraine after the Chernobyl nuclear accident: statistical data and clinicomorphologic characteristics.

BACKGROUND: The increase in the number of childhood thyroid carcinoma cases in Ukraine after the Chernobyl nuclear accident in 1986 prompted the development of a registry of thyroid carcinoma cases at the Institute of Endocrinology and Metabolism in Kiev. In the current study, the authors report the statistical data and clinicomorphologic features of the cases included in this registry. METHODS: To study the incidence, and age and gender distribution of thyroid carcinoma in Ukraine, the authors compiled complete clinical information from cases diagnosed and treated at the Institute of Endocrinology and Metabolism and statistical reports submitted to the registry from 27 regions of Ukraine. Morphologic features of the resected tumors were examined and were included in the database. RESULTS: During the 5 years preceding the Chernobyl nuclear accident, a total of 59 cases of thyroid carcinoma were identified in the birth to 18 years age group (25 in children age < or = 14 years and 34 in adolescents ages 15-18 years). Between 1986 and 1997, the total number of thyroid carcinomas in Ukrainian children and adolescents was 577 (358 children and 219 adolescents). Morphologically, the thyroid tumors overwhelmingly were papillary carcinomas, and the majority of these also showed a follicular and/or solid growth pattern. Lymph node metastases and other extrathyroidal spread were common, thus necessitating total thyroidectomy and lymph node dissections in many patients. CONCLUSIONS: Between 1990 and 1997, a significant increase in the incidence of thyroid carcinoma was noted in children and adolescents in Ukraine; the group most affected was comprised of the individuals who were age < or = 5 years in 1986 (the year of the Chernobyl nuclear accident). The largest number of cases occurred in patients living in areas of thyroid radiation doses of > or =0.50 grays. The morphologic features of those thyroid tumors suggest that they are aggressive tumors with a high frequency of lymph node metastases, venous invasion, and extrathyroidal spread.