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Reference values for thyroid volume established by ultrasound in Polish schoolchildren.

INTRODUCTION
A frequency in excess of 5% of goitre in children is an approved WHO marker of iodine deficiency. As thyroid ultrasound remains the main method of thyroid volume (TV) assessment, the choice of adequate normative values is important for the proper interpretation of epidemiologic data. There is disagreement as to whether local or international normative values should be used. The aim of this study was to establish Polish local TV normative values in children aged 6-12 years.


MATERIAL AND METHODS
The study was carried out in a group of 642 children aged 6-12 years (312 girls and 330 boys) living in the Polish seaside area with a proven history of best iodine supply. Inclusion criteria were: iodine concentration in casual morning urine samples above 100 μg/L, no goitre on palpation, no pathological findings on thyroid US, no history of thyroid disorders, no treatment affecting thyroid function, and written informed consent from the child's parents. TV was measured ultrasonographically with a 7.5 MHz linear transducer. Urinary iodine concentration (UIC) was measured in urine spot samples using the Sandell-Kolthoff method.


RESULTS
Median UIC ranged according to age from 126.6 to 155.1 μg/L in girls, and from 132.23 to 157.62 μg/L in boys. TVs at P97 were: 3.96, 4.23, 4.33, 5.44, 6.07, 9.5, and 10.9 for girls and 3.99, 4.2, 4.79, 6.61, 7.38, 7.89, and 9.35 for boys. They were lower than the 1997 WHO normative values but higher than the 2004 reference currently adopted by the WHO.


CONCLUSIONS
The obtained results may be adopted as normative TV values for Polish children.