Iodine deficiency in urban primary school children: a cross-sectional analysis.

OBJECTIVE To determine the prevalence of iodine deficiency in primary school children in an Australian urban population. DESIGN AND SETTING A cross-sectional survey of school children aged 5-13 years attending a public school on the Central Coast of New South Wales in November 2000. PARTICIPANTS 324 (70%) of the 465 children enrolled in the school (180 boys; 144 girls). MAIN OUTCOME MEASURES Thyroid volumes compared with World Health Organization/International Council for the Control of Iodine Deficiency Disorders (WHO/ICCIDD) thyroid volume reference values. Iodine status based on WHO/ICCIDD urinary iodine concentration (UIC) categories (normal, >/= 100 microg per litre of urine [microg/L]; mild iodine deficiency, 50-99 microg/L; moderate deficiency, 20-49 microg/L; severe deficiency, < 20 microg/L); not more than 20% of the population should have a UIC below 50 microg/L. RESULTS Median UIC for school children was 82 microg/L, and 14% of children had UICs below 50 microg/L. Thyroid volume reference values indicated a prevalence of goitre of zero. In girls, only four (3%) and one (1%) had thyroid volumes above the WHO/ICCIDD medians by age and body surface area (BSA), respectively (P < 0.001). In boys, three (2%) and one (1%) had thyroid volumes above WHO/ICCIDD medians by age and BSA, respectively (P < 0.001). CONCLUSION Despite the median UIC being less than ideal, most children were not goitrous. This underscores the importance of using physiological outcome measures in areas where iodine deficiency is marginal before concluding the need for iodine supplementation based purely on median UIC. We call for a systematic national survey to determine iodine status using a combination of iodine deficiency indicators.