Monitoring iodine in school children of villages in northwest of Tehran ten years after iodine supplementation

This study was carried out in order to monitor the iodine supplementation programme in school children of Kiga, Keshar, Randan in northwest of Tehran. All inhabitants of these villages had received iodized oil injection (containing 480mg iodine) in 1989 and continued with consumption of iodized salt ever since. In this study, 250 students from these villages aged 6-14 years were studied. Goiter grade was examined by palpation and graded according to WHO classification. Thyroid hormone concentrations were determined by commercial kits and urinary iodine was measured by digestion method. The results were compared with data of our previous study in 1989. Goiter prevalence decreased 40.5% as compared with 1989. Grade 2 goiter in 1989 and 1999 were, 94.5 and 14.3% in Kiga 66 and 9.4% in Keshar 82 and 9.7% in Radan, respectively, (P<0.001). Median urinary iodine excretion in 226 students was 18.6±6.1μg/dL that showed a significant increase from 1989 to 1999, (P<0.001). Serum T4, T3, TSH, T3Rup, FT4I in 232 students were in normal ranges. The mean hormone levels in 1989 and 1999 were: T4: 6.5±2 and 8.4±1.6μg/dL T3: 177±38 and 145±29 ng/dL TSH: 10.8±15.1 and 1.8±0.8 μU/mL, respectively P<0.001. No correlation was established between thyroid hormones, urinary iodine and goiter grade. These finding demonstrate that iodine supplementaion programme in rural areas with severe iodine deficiency has caused a significant decrease in the prevalence of goiter and a significant increase in urinary iodine excretion, along with correction of hypothyroidism.