New reference values for thyroid volume by ultrasound in Semirom, Iran: Report of a pilot study

Background and Objective: Physical examination (inspection and palpation) has been the only available method to estimate thyroid size for many years. In areas of mild iodine deficiency, where goiters are small, ultrasonography is preferable compared to palpation for estimating thyroid volume and goiter prevalence. The proper interpretation of ultrasonography requires local reference values for thyroid volume. Our objective was to define local normal values for thyroid volume by ultrasound in school-age children in Semirom, Iran.Methodology: One thousand eight hundred twenty eight (1828) school children were enrolled in the study. Thyroid size was estimated in each child by inspection and palpation by an expert endocrinologist and was graded according to the WHO s classification. Ninety five children were randomly selected to perform ultrasound. Age specific 97 percentiles for thyroid volume were calculated for boys and girls.Results: The mean age was 9.12 ± 0.98 (mean ± SD). The prevalence of goiter by palpation in 1828 school children was 36.7%. 35% of boys and 38.6% of girls were considered goitrous by palpation. The average thyroid volume was 3.46 ± 0.13 ml. In girls, the mean of thyroid volume was 3.47 ± 0.12 ml, while it was 3.45 � 0.15 ml in boys (p = 0.18). The regional 97 percentile of thyroid volume by ultrasound was much lower than the WHO s reference values.Conclusion: Similar to some other studies, the present study showed that the local reference is preferred for proper assessment and interpretation of thyroid volume, particularly in developing countries