Are Australian children iodine deficient? Results of the Australian National Iodine Nutrition Study

Abstract

Objective: To document the population iodine nutritional status in Australian schoolchildren. Design and setting: Cross‐sectional survey of schoolchildren aged 8–10 years, based on a one‐stage random cluster sample drawn from all Year 4 school classes in government and non‐government schools in the five mainland Australian states of New South Wales, Victoria, South Australia, Western Australia and Queensland. The study was conducted between July 2003 and December 2004. Participants: 1709 students from 88 schools (881 boys and 828 girls), representing 85% of the estimated target number of students. The class participation rate was 65%. Main outcome measures: (i) Urinary iodine excretion (UIE) levels (compared with the criteria for the severity of iodine deficiency of the World Health Organization/International Council for the Control of Iodine Deficiency Disorders: iodine replete, UIE ≥ 100 μg/L; mild iodine deficiency, UIE 50–99 μg/L; moderate iodine deficiency, UIE 20–49 μg/L; severe iodine deficiency, UIE < 20 μg/L); (ii) Thyroid volumes measured by ultrasound (compared with new international reference values). Results: Overall, children in mainland Australia are borderline iodine deficient, with a national median UIE of 104 μg/L. On a state basis, NSW and Victorian children are mildly iodine deficient, with median UIE levels of 89 μg/L and 73.5 μg/L, respectively. South Australian children are borderline iodine deficient, with a median UIE of 101 μg/L. Both Queensland and Western Australian children are iodine sufficient, with median UIE levels of 136.5 μg/L and 142.5 μg/L, respectively. Thyroid volumes in Australian schoolchildren are marginally increased compared with international normative data obtained from children living in iodine sufficient countries. There was no significant association between UIE and thyroid volume. Conclusion: Our results confirm the existence of inadequate iodine intake in the Australian population, and we call for the urgent implementation of mandatory iodisation of all edible salt in Australia.

Increasing thyroid cancer incidence in Queensland, Australia 1982–2008 – true increase or overdiagnosis?

“…Both iodine deficiency and improved iodine nutrition have been suggested potential risk factors for thyroid cancer; however, iodine levels in Queensland are considered to be sufficient. 35 Finally, while more frequent use of diagnostic imaging may be contributing to increasing ascertainment of indolent thyroid cancers, it is also possible that increasing exposure to radiation from greater use of diagnostic imaging, particularly in children, 36 is contributing to a real rise in the disease. While none of these factors is likely to individually explain the large increase in thyroid cancer, these (and potentially factors as yet to be identified) may be working in concert with overdiagnosis to increase rates.…”

Iodine deficiency in industrialized countries*

“…By 2001, median iodine content of milk samples in Sydney had fallen to 140 lg/l. In 2004, a national survey 8 found that children in south-eastern Australia were iodine deficient and 9% of girls had goitre by thyroid ultrasound, leading to the introduction of a national programme in 2009 to iodize all salt used in bread making.…”

Low urinary iodine postpartum is associated with hypothyroid postpartum thyroid dysfunction and predicts long-term hypothyroidism

“…The correlation between low urinary iodine and PPTD or progression to hypothyroidism in our study is unlikely to be secondary to dietary iodine deficiency, as an Australia-wide survey has found Western Australia to be an iodine sufficient region with a median (interquartile range) UIC of 142AE5 lg/l (103AE5-214AE0). 17 A more recent survey of women in the first trimester in Western Australian has also confirmed the state to be iodine replete. 18 In this study, median UIC was 182 lg/l (95%CI: 156-204).…”

“…By comparison, the median urinary iodine concentration (quartiles) in Western Australia from the nationwide survey was 142AE5 (103AE5, 214AE0) lg/l. 17 UIC < 50 lg/l. Using threshold UIC concentrations, a low UIC was predictive of hypothyroidism at 12-year follow-up at <100 lg/ l (P = 0AE03) and at <50 lg/l (P = 0AE02).…”