The Effects of Dual Micronutrient Supplementation on Thyroid Function in School Children: An Experimental Study

Background : The presence of iron and or vitamin A deficiency in children limits the effectiveness of the iodine intervention program in areas where iodine deficiency is endemic. This study was aimed at assessing the role of dual micronutrient supplementation on thyroid function in severe iodine deficient school children age 6-16 years in Ethiopia.
Methods: From 2006 to 2007 an experimental study was conducted on 397 children, all with visible goiter grade of which 6.1% and 10.3% vitamin A and iron deficient respectively. A week after baseline data collection and de-worming, all children with visible goitre (n=332) but without iron and vitamin A deficiency were randomly grouped into four, A to D groups. Vitamin A deficient children (n=24) were randomly allocated to group A and group B while anaemic children (n=41) were distributed into group C and group D. Group A received 400mg oral iodized oil and group B received 200,000IU vitamin A plus 400mg oral iodized oil. Group C received 400mg oral iodized oil while group D received 100mg iron sulphate with folic acid and 400 mg oral iodized oil. Iron supplementation was continued two doses per day for six weeks. Vitamin A supplemented group received additional dose at six month. Post intervention data on iodine, vitamin A and iron status were collected at 6 and 11 month.
Results: Children supplemented with iron + oral iodized oil capsule had significant goitre reduction than oral iodized oil supplemented group. The mean concentrations of thyroid hormone (T4) and Urinary iodine excretion (UIE) in iron + iodine supplemented group were significantly higher than the iodine alone supplemented group at 6 months after the intervention. Hemoglobin level at baseline in all study subjects and at 11 month after intervention in group D (iron + iodine supplemented group) significantly (P<0.05) correlated with T4 level. The significant goitre reduction in iron + iodine supplemented group than iodine alone supplemented group and significant correlation between level hemoglobin and T4 at baseline and at 11 month after intervention probably indicate that iron and iodine have a functional interaction in thyroid iodine metabolism.
Conclusion: Supplementation of iodized oil with Iron is more effective in goitre reduction than iodine alone and this should be taken into consideration by iodine deficiency disorders (IDD) intervention programs.