Timing of the Effect of Iodine Supplementation on Intelligence Quotients of Schoolchildren


avatar Salarkia N 1 , avatar Mirmiran P 1 , avatar Azizi F 1 , *

Endocrine Research Center, National Nutrition and Food Technology Research Institute, Shaheed Beheshti University of Medical Sciences, [email protected], IR Iran

how to cite: N S, P M, F A. Timing of the Effect of Iodine Supplementation on Intelligence Quotients of Schoolchildren. Int J Endocrinol Metab.2(2): -.


Iodine deficiency is the most important preventable cause of mental deficiency. The aim of this study was to specify the phase during fetal and postnatal development when iodine supplementation would have optimum effect on the prevention of brain damage.

Materials and Methods:

Forty schoolchildren aged 7-13 years, from the previously iodine deficient villages of Kiga and Randan, were divided into 3 subgroups: in subgroup I the mother had received iodized oil 1-4 years prior to conception and infant consumed iodized salt from the age 14 years onwards; in subgroup II mothers received iodized oil during pregnancy and the child received iodized salt from the age 2-4 years and in subgroup III the child received iodized oil injection from age 1-3 and iodized salt from 3-6 years of age onwards. Serum T4, T3, TSH and TJ uptake and urine iodide concentrations were measured. Bender-Guestalt and Raven tests were employed for psychomotor evaluation. A group of 40 age and sex matched schoolchildren from Tehran served as controls.


Mean age of subgroups I, II and III were 8.91.7, 9.41.4 and 1l.91.2 years, respectively. Serum T4, T3, TSH and urinary iodine concentrations were normal in all children. Urinary iodine and serum T4, T3 and TSH concentration did not differ between the 3 subgroups. Mean IQ was higher in subgroup I (1027), as compared to subgroup II (9310, p<0.002) and subgroup III (9S10, p<0.0S). Mean IQ of subgroup I was not significantly different from age-matched controls, but a significant decrease in IQ was evident in subgroups II (9310 vs 1098, p<0.002) and III (9610 vs 11411,p<0.001 ), as compared to the control children.


It is concluded that children whose mothers received iodide supplementation before conception had normal IQs of significantly higher values than those whose mothers received iodine during pregnancy and the children who received iodine after birth.

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