Thyroid Research Thyroid Research Archive Iodine

Recurrence of mild iodine deficiency in Tasmania

(November 2002)

The background of the study. Endemic goiter was common before 1950 in Tasmania. Then, iodine intake was increased by the distribution of potassium iodide tablets to schoolchildren, and later by the addition of potassium iodate to bread and the use of iodine-containing disinfectants in dairy cattle. The government then mandated an upper limit for iodine content in milk, and the addition of potassium iodate to bread ceased. By the 1990s, as dairy-farming practices changed, some children had urinary iodine values <50 µg/L, indicative of moderate dietary iodine deficiency. This study was undertaken to evaluate iodine nutrition in Tasmania 50 years after iodine supplementation was introduced.

How the study was done. The study subjects were 225 children (99 girls, 126 boys; mean age, 11 years). Morning urine samples were collected for the measurement of iodine, and thyroid volume was measured by ultrasonography.

The results of the study. The median urinary iodine excretion was 84 µg/L in the 225 children, and 20 percent had values of 50 µg/L or lower, indicative of moderate iodine deficiency. The prevalence of thyroid enlargement in the girls and boys was 21 percent and 22 percent, respectively, based on age and body-surface area. There were no differences in thyroid volume in the girls and boys, or among children living in different areas of the state or having different socioeconomic status.

The conclusions of the study. The values for urinary iodine excretion and the frequency of thyroid enlargement indicate the recurrence of mild iodine deficiency in Tasmania.

The original article. Guttikonda K, Burgess JR, Hynes K, Boyages S, Byth K, Parameswaran V. Recurrent iodine deficiency in Tasmania, Australia: a salutary lesson in sustainable iodine prophylaxis and its monitoring. J Clin Endocrinol Metab 2002;87:2809-15.

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Iodine

• Iodine deficiency is a major health problem worldwide