Iodine intake in an urban environment: a study of urine iodide excretion in Auckland.

Dietary iodine intake was estimated by measurement of iodide in random overnight 12 hr and 24 hr urine samples. Urinary iodide excretion was measured in 231 healthy females comprising 127 female secondary students (ages 16-19), 27 female tertiary students (17-23 yr), 42 female laundry workers (18-52 yr) and 26 pregnant women in the third trimester (18-40 yr). Urine iodide excretion was also examined in a group of 28 patients attending a thyroid clinic, with thyroid disease of diverse aetiology and in 34 patients taking the antiarrhythmic drug amiodarone for control of cardiac arrhythmias. The mean daily urine iodide excretion was 2.4 mumol/day (0.9-5.8 mumol/day) and iodide to creatinine ratio 0.21 mumol/mmol (0.09-0.29). Iodine deficiency (less than 0.4 mumol/day) was not observed in any subject. Excessive iodine (greater than 8 mumol/day) was found only in patients known to be taking iodine-containing drugs and in one normal individual. The urine iodide was normal in 154 female students, 14 of whom had a trivial thyroid enlargement. The study suggests that dietary sources other than iodised salt contribute significantly to dietary iodine intake and that residual goitre in the community is not secondary to deficiency or excess of dietary iodine.