More Than a Decade of Iodine Prophylaxis Is Needed to Eradicate Goiter Among School Age Children in a Moderately Iodine-Deficient Region

Abstract

There are many studies regarding the effect of iodine supplementation on goiter, but relatively few reports on the duration of iodine supplementation required to eradicate goiter in iodine-deficient regions. In the current study, we aimed to determine goiter prevalence as determined by sonographic methods, as it relates to changes in median urinary iodine concentrations (UIC) among school age children (SAC), ages 9-11. This study was performed in Ankara, Turkey, before and 5-10 years after mandatory iodination of table salt. Three hundred to 400 SAC from the same primary schools were studied every year by measurement of UIC as part of Turkish Iodine Surveys. Sonographically determined thyroid volume of the SAC had been measured before the mandatory iodination in 1997 and 5-10 years afterward, in 2002 and 2007. The prevalence of goiter in children was evaluated using World Health Organization/International Council for the Control of Iodine Deficiency Disorders recommendations for age and sex. Moderate iodine deficiency was present in 1997 (median UIC, 25.5 microg/L), and it improved to mild iodine deficiency in 2001 (median UIC, 87 microg/L). Sufficient iodine intake (median UIC, 117 microg/L) was achieved by the year 2004. Goiter prevalence was 25% in 1997, 12.3% in 2001, and decreased to 1.3% in 2004. The time required to normalize the prevalence of goiter in SAC living in a moderately iodine-deficient environment was at least a decade. To achieve a goiter rate of less than 5% among SAC, it may require that, as a population, they were born and grew up under conditions of iodine sufficiency.