Validation of established thyroid ultrasound volume norms in a Chernobyl cohort.

OBJECTIVE

To establish thyroid ultrasound volume norms appropriate for studies of diffuse goiter in a cohort of children and adolescents from an iodine-deficient population exposed to 131I by the Chernobyl fallout.

METHODS

A cohort of 11,970 Belarusians aged ≤18 years at the time of the 1986 Chernobyl accident with individual thyroid radiation dose estimates was screened 10-18 years later. From these, a low-dose subset of 2,392 with no thyroid diseases was selected to construct age- and sex-specific normative values for thyroid ultrasound volume, compared to Belarusian Ministry of Health (MOH) norms and existing WHO and European standards.

RESULTS

Cohort-specific values were generally lower than MOH norms and WHO standards for 11-17-year-olds. For those aged ≥18 years, internal norms were 30% higher in males and 15-30% lower in females than MOH norms, and exceeded European values for both sexes. Thyroid volume norms were about 40% higher in males and 30% higher in females as a function of BSA compared to European values. Thyroid volume continued to increase in both sexes, and by age 30-34 years, cohort-specific norms were 6% higher in males and 26% higher in females than European values. Urinary iodine concentration did not significantly explain variance in thyroid volume beyond sex, age, and BSA.

CONCLUSIONS

In this iodine-deficient cohort of young Belarusians exposed to 131I by Chernobyl fallout, thyroid ultrasound volumes differed substantially from MOH norms and established WHO standards, prompting a revision of diffuse goiter definition using cohort-specific normative values.