Effect of iodine supplementation on a pediatric population with mild iodine deficiency

A cross-sectional study in two stages consisted of healthy children to asse ss the effect of iodine supplementation on a pediatric population with mild iodine deficiency in an ongoing program in the Province of Pontevedra, nor thwestern Spain. In the first survey (1984), 1565 schoolchildren and in the second survey (1995) 907 schoolchildren were randomly selected from the po pulation. In January 1985, a mandatory consumption of iodized salt in our r egion was begun. In both surveys we studied prevalence of goiter, urinary i odine excretion, and prevalence of thyroid dysfunction. Similar prevalences of goiter were observed in both surveys, 3.7% versus 3.9%; however, signif icantly lower prevalence of Ib and II degree goiters were observed in the s econd survey. The mean iodine excretion was 88.6 +/- 73 mu g/L (median 66.3 ) and 146.4 +/- 99 mu g/L (median 115.7), p < 0.01 for the first and second surveys, respectively. Finally, the overall prevalence of thyroid dysfunct ion was similar in both surveys, 9.2% versus 7.0%; however, significantly l ower prevalence of suppressed serum thyrotropin (TSH), considered as a mark er of subclinical hyperthyroidism, was observed in the second survey when c ompared to the first, 0.1% versus 2%, p < 0.01. Our results are in agreemen t with the recent data from Denmark, where the prevention of subclinical hy perthyroidism occurring in the elderly as a consequence of longstanding mil d iodine deficiency is the reason that the Danish finally started iodine su pplementation on a national basis. In conclusion, long-term correction of m ild iodine deficiency in a pediatric population has beneficial effects on t he prevalence of high-degree goiters, and this correction reduces significa ntly the prevalence of subclinical hyperthyroidism. The present observation constitutes a strong argument for correcting even mild iodine deficiency.