Abstract
Objective: The purpose of this study was to evaluate the effect of 10 years iodine supplementation on the IDD impact indicators in the iodine deficient schoolchildren of villages north of Tehran.
Methods: In 564 schoolchildren aged 6-15 years, goiter was graded according to the WHO classification, serum thyroid hormones and TSH concentrations and urinary iodine excretion were measured and Raven and Bender-Gestalt tests were employed before and 10 years following iodine supplementation.
Results: A significant decrease in grade 2 goiters concomitant with an increase in grade 1 goiter was seen (P<0.001) and goiter rate decreased by 42%. The studied variables before and ten years after iodine supplementation were: median urinary iodine excretion 2.0 vs.19.0 µg/dL, P<0.001; T4: 6.5± 2.0 vs. 8.4±1.6 µg/dL, P<0.001, T3: 177±38 vs. 145±29 ng/dL, P<0.001; TSH: 10.8±15.1 vs. 1.8±0.8 µU/mL, P<0.001; IQ: 93.8±5.4 vs. 100.3±4.1, P<0.01; difference between chronological and psychomotor age was 2.1 and 1.6 years, p<0.001, before and after intervention. Children whose mothers received iodine supplementation before conception had significantly higher IQ than those whose mothers received iodine during pregnancy and the children who received iodine after birth (102±7, 93±10 and 95±10, respectively; p<0.02).
Conclusion: Sustained iodine supplementation improves impact indicators of iodine nutrition. The effect on IQ and psychomotor development of offsprings is more enhanced when iodine supplementation begins before conception.