Iodine deficiency in adolescents from Bombay slums.

BACKGROUND. Iodine deficiency may be associated with endemic goitre, lowered levels of circulating thyroid hormone and suboptimal brain function. We studied iodine deficiency, thyroid status and scholastic performance in 866 (416 girls and 450 boys) adolescents from the slums of Bombay. METHODS. We examined 866 adolescents (416 girls and 450 boys) to determine the presence of goitre. Circulating levels of T3 and T4 were estimated by radioimmunoassay and of thyroid stimulating hormone by the immunoradiometric assay technique. Their scholastic performance was assessed by the average marks obtained in the last examination. RESULTS. The prevalence of goitre was 56% in both boys and girls. The visible goitre rate was also similar in boys (9.8%) and girls (10.6%). We found no significant difference in the mean urinary iodine excretion and urinary iodine to creatinine ratio between boys and girls, but the mean serum T3 and T4 levels were lower in girls than in boys, while the thyroid stimulating hormone levels were higher. The mean thyroid hormone levels were consistent with normal thyroid function. With an increase in the size of goitre, there was a decrease in urinary iodine excretion, urinary iodine to creatinine ratio, T3 and T4 levels while the thyroid stimulating hormone levels increased. The scholastic performance of the adolescents with goitre was poor. Forty-eight per cent of them obtained less than 50% marks and their academic grades showed a significant association with thyroid stimulating hormone levels. CONCLUSION. Goitre has a high prevalence among adolescents in the slums of Bombay. This can be attributed partly to the increasing demand for iodine at puberty which cannot be satisfied with the limited amounts available in food. The children also show a poor scholastic performance. Mild iodine deficiency can be easily controlled by encouraging the use of iodized salt in adolescents.