Sustainability of a well-monitored salt iodization program in Iran: Marked reduction in goiter prevalence and eventual normalization of urinary iodine concentrations without alteration in iodine content of salt

Objective: Two yr after legislation of salt iodization of 40 parts per million (ppm) in 1994, goiter was still endemic and urinary iodine concentration (UIC) remained elevated in many provinces of Iran. Goiter prevalence and UIC were compared 2 and 7 yr after sustained consumption of uniformly iodized salt by Iranian households. Methods: Schoolchildren (7-10 yr) of all provinces were randomly selected by cluster sampling from December 2000 to June 2001. Goiter rate, UIC, and household salt iodine values were compared to those in 1996. Factory salt iodine was also compared in 2001 vs 1996. Ultrasonographically determined thyroid volumes of 7-10 yr old children were compared in 2001 vs 1999. Results: In 2001 (no.=33600) vs 1996 (no.=36178), total, grade 1, and grade 2 goiter rates were 13.9 vs 53.8%, 11.0 vs 44.8%, and 2.9 vs 9.0%, respectively (p<0.0001). Weighted total goiter rate was 9.8% in 2001. Median (range) UIC in 2001 (no.=3329) was 165 (18-499) mu g/l and in 1996 (no.=2917) was 205 (10-2300) mu g/l (p<0.0001). In 2001 vs 1996, mean+/-SD for iodine salt content was 32.7+/-10.1 vs 33.0+/-10.2 ppm (p=0.68) in households and was 33.2+/-13.4 and 33.8+/-13.2 ppm (p=0.57) in factories, respectively. Among 7-10 yr old children in 2001 (no.=400) vs 1999 (no.=396), only 7-yr-old children in 2001 (the only group with probably no history of iodine deficiency) showed significant smaller thyroid volumes by ultrasonography compared to those in 1999. Conclusions: After 7 yr of optimized iodized-salt supplementation in Iran, adequate UIC values and marked reduction in goiter rate have been achieved.