Iodine status of New Zealand residents as assessed by urinary iodide excretion and thyroid hormones.
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, seventy-seven 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 microgram/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.
Thomson
C D
CD
Department of Human Nutrition, University of Otago, Dunedin, New Zealand.
Colls
A J
AJ
Conaglen
J V
JV
Macormack
M
M
Stiles
M
M
Mann
J
J
D000293:Adolescent; D000328:Adult; D000368:Aged; D003404:Creatinine / Q000652:urine; D003627:Data Interpretation, Statistical; D005260:Female; D006304:Health Status; D006801:Humans; D007454:Iodides / Q000652:urine*; D007455:Iodine / Q000008:administration & dosage / Q000172:deficiency / Q000378:metabolism*; D008297:Male; D008875:Middle Aged; D009520:New Zealand; D012044:Regression Analysis; D012306:Risk; D013963:Thyroid Hormones / Q000652:urine*; D013974:Thyroxine / Q000652:urine; D014284:Triiodothyronine / Q000652:urine
D007454:Iodides; D013963:Thyroid Hormones; D014284:Triiodothyronine; D007455:Iodine; D003404:Creatinine; D013974:Thyroxine