Thyroid examination in highly radiation-exposed workers after the Chernobyl accident.

Context: Radioactive contamination from the Chernobyl nuclear accident which happened in the morning of 26 April 1986 had a major impact on thyroid health in the Belarus region. Objective: Observational study of a cohort of 99 adults, most strongly exposed to ionizing radioactivity. Design, Setting, and Patients: Observational study performed between 1998 and 2000. The cohort was comprised of 99 workers (92 male) of the Chernobly nuclear power plant. Examination including physical examination, ultrasonography of the thyroid gland and measurement of serum free thyroxin (fT4), free triiodothyronine (fT3), and thyroid stimulating hormone (TSH). Anti-TPO, anti-Tg antibodies and TSI were also determined. Main Outcome Measures: The impact of exposure to high dose radiation, including radioactive iodine, on the thyroid gland was examined. Results: Levels of fT4 in all probands were within the normal World Health Organization-defined range. Elevated levels of fT3 were found in two workers (2%), high titres of anti-TPO and anti-Tg antibodies was present in four subjects (4%). Mild hypothyroidism was present in one patient. Enlargement of the thyroid gland was observed in 17 workers (17%). There was no evidence of clinically overt thyroid cancer. Conclusions: The Chernobyl accident showed surprisingly little impact on the thyroid in a cohort of workers strongly exposed to radiation. Our data suggest an age-dependent heterogeneity in the response to short-lived radioiodine isotopes and favors long-term follow-up analysis.