Marked Reduction in Goiter Prevalence and Eventual Normalization of Urinary Iodine Concentrations in Iranian Schoolchildren, 10 Years After Universal Salt Iodination

Two years 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 two and seven years after sustained consumption of uniformly iodized salt by Iranian households. From December 2000 to June 2001, schoolchildren (7-10 yr) of all provinces were randomly selected by cluster sampling their goiter rate, UIC, and household salt iodine levels were compared to similar data collected in 1996. Factory salt iodine produced in 2001 was also compared to that of 1996. Ultrasonographically determined thyroid volumes of 7-10 yr old children were compared in 2001 to thoese of 1999. Total, grade 1, and grade 2 goiters were 13.9 vs. 53.8%, 11.0% vs. 44.8%, and 2.9% vs. 9.0%, in 2001 (n=33600) vs. 1996 (n=36178), respectively (p<0.0001). Median (range) UIC in 2001 (n=3329) was 165 (18-410) µg/L and in 1996 (n=2917) was 205 (10-2300) µg/L (P<0.0001). Means for iodine salt content were 32.7±10.1 and 33.0±10.2 (P=0.79) in households and 33.2±13.4 and 33.8±13.2 (P=0.67) in factories, in 2001 and 1996, respectively. Only 7-yr-old children in 2001 (the only group with probably no history of iodine deficiency) showed significantly smaller thyroid volumes compared to those in 1999. After seven years of optimized iodized-salt supplementation in Iran, adequate UIC values and marked reduction in goiter rate have been achieved.