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Iodine status of New Zealand residents as assessed by urinary iodide excretion and thyroid hormones

Published online by Cambridge University Press:  09 March 2007

Christine D. Thomson ,
Andrew J. Colls ,
John V. Conaglen ,
Matthew Macormack ,
Martin Stiles  and
Jim Mann
Christine D. Thomson
Affiliation:
Department of Human Nutrition, University of Otago, PO Box 56, Dunedin, New Zealand
Andrew J. Colls
Affiliation:
Department of Human Nutrition, University of Otago, PO Box 56, Dunedin, New Zealand
John V. Conaglen
Affiliation:
Department of Medicine, Waikato Hospital, Hamilton, New Zealand
Matthew Macormack
Affiliation:
Department of Human Nutrition, University of Otago, PO Box 56, Dunedin, New Zealand
Martin Stiles
Affiliation:
Department of Medicine, Waikato Hospital, Hamilton, New Zealand
Jim Mann
Affiliation:
Department of Human Nutrition, University of Otago, PO Box 56, Dunedin, New Zealand
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Abstract

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The aims of this study were (1) to compare various measures of I status, and (2) to assess urinary I and thyroid hormone status of residents of two areas of New Zealand where, before the iodization of salt, goitre was endemic due to low soil I. A total of 189 subjects (102 males, eighty-seven females) were recruited from the Dunedin Blood Transfusion Centre, and 144 (sixty-seven males, seventyseven females) from the Waikato Blood Transfusion Centre between November 1993 and June 1994. Blood was taken for thyroid hormone assays, and subjects collected a fasting overnight urine specimen, a double-voided fasting urine sample, and a complete 24 h specimen for iodide and creatinine analyses. Positive correlations (P < 0.0001) between daily iodide excretion and iodide concentrations in fasting and double-voided fasting urines, identical median values for iodide concentrations in the three samples, and similar numbers of subjects classified as at risk from I deficiency disorders according to the International Committee for the Control of Iodine Deficiency Disorders/World Health Organization categories (World Health Organization, 1994) confirmed indications from earlier studies that fasting urine samples were suitable for population studies. However 24 h urinary iodide excretion remains the recommended measure for individual I status. Waikato residents excreted more iodide in urine and all measures were significantly greater than for Otago residents. However median urinary iodide excretions for both areas (60 and 76 μg/d for Otago and Waikato respectively) were considerably lower than those reported previously for New Zealand. Thyroid hormone concentrations were within normal ranges. Our findings suggest that I status of New Zealanders may no longer be considered adequate and may once again be approaching levels of intake associated with clinical I deficiency.

Keywords

IodineThyroid hormonesNew Zealand
Type
Human and Clinical Nutrition
Information
British Journal of Nutrition , Volume 78 , Issue 6 , December 1997 , pp. 901 - 912
Copyright
Copyright © The Nutrition Society 1997

References

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