Association of ferritin with goiter, urinary iodine and serum thyroid hormones in schoolchildren of Iran

Iodine deficiency disorders are usually found in the countries with malnutrition problems. One of the most important problems of malnutrition is iron deficiency, which can affect thyroid metabolism and it may decrease the effect of iodine supplementation. This is a cross-sectional study to determine serum ferritin concentration and its association with the prevalence of goiter, urinary iodine and thyroid function. Schoolboys and girls aged 8-10 years were equally and randomly selected from 26 provinces of the country. In total, 36178 schoolchildren were assessed for goiter. Blood and urinary samples were taken randomly from 10% of the subjects for the measurement of T4, T3, TSH, T3RU, ferritin and urinary iodine. The prevalence of goiter was more than 50% in 6, 40-50% in 7 and less than 40% in 13 provinces. Changes in ferritin concentration in these 3 groups of provinces were not statistically significant. The median urinary iodine excretion was more than 50 in 4, 30-40 in 2, 20-29 in 11 and 13-20 μg/dl in 9 provinces. The mean serum ferritin value was higher in the provinces where the median urinary iodine value of schoolchildren was desirable (13-20 μg/dl) than the provinces where the median urinary iodine value of schoolchildren was more than 20 μg/dl (P<0.001). There was a significant difference in the prevalence of goiter in schoolchildren with serum ferritin above 10 μg/dl and those with serum ferritin below 10 μg/dl (20% vs. 80%, P<0.0001). Serum ferritin was significantly correlated with T3RU, T3 and FT3I (P<0.05). The data shows that goiter is more prevalent in schoolchildren with low serum ferritin, but there is an unimportant change in thyroid function. Low serum ferritin may impair the efficacy of iodized salt supplementation in reducing goiter size. Therefore, we suggest that iodized salts with Dextran-coat should be considered in the national IDD program.