Thyroid volume and echostructure in schoolchildren living in an iodine-replete area: relation to age, pubertal stage, and body mass index

Abstract

Background: Thyroid volume (TV) varies between geographical regions. Thus, population-specific references for TV in regions with long-standing iodine sufficiency may be more accurate than a single international reference.

Aim: The aim of the study was to determine TV and assess the prevalence of goiter and thyroid nodules in schoolchildren aged 5-18 years living in an iodine-replete area.

Methods: Ultrasonography was used to assess TV and structure in 440 schoolchildren (200 boys and 240 girls) living in the Athens area. Urinary iodine excretion was also measured. Age, body surface area (BSA), body mass index (BMI), and Tanner stage were recorded.

Results: TV was significantly correlated with age in boys (r = 0.779, p < 0.0005) and girls (r = 0.669, p < 0.0005), and with BSA in boys (r = 0.730, p < 0.0005) and girls (r = 0.623, p < 0.0005). TV increased with the progress of puberty in boys (Tanner stage I: 3.42 mL; Tanner stage II-V: 7.35 mL; p < 0.0005) and girls (Tanner stage I: 3.74 mL; Tanner stage II-V: 5.99 mL; p < 0.0005). We used the 97th percentile value as the upper limit and calculated the prevalence of goiter to be 3.2%. There was a weak correlation between TV and BMI standard deviation score only in boys (r = 0.166, p = 0.023). Boys in Tanner stage II-V had larger TV than girls had in the same pubertal stage (7.35 mL vs. 5.99 mL, p = 0.001); such a difference was not observed in Tanner stage I. The median urinary iodine was 307.83 microg I/g creatinine, indicating iodine sufficiency. There was a significant inverse correlation between TV and urinary iodine. In 5.1% of the studied subjects one or more nodules were observed, whereas in 4.1% of cases the nodules were accompanied by hypoechogenicity.

Conclusions: In healthy Greek children living in an iodine-replete area, the main determinants of TV in both boys and girls were age, BSA, and pubertal stage. The prevalence of goiter was 3.2% and that of altered echostructure was 9.2%.