Serum T4 , T3 and TSH and Urinary Iodine Levels in Schoolchildren of 26 Provinces of I.R. Iran

Endemic goiter and iodine deficiency disorders (IDD) are prevalent in Iran and IDD control program has been implemented since 1989. To monitor IDD control program, this survey was performed in 1996. 26178 schoolchildren, aged 8 to 10 years were selected by probability proportionate to size randomly in 26 provinces of Iran, for goiter staging. In 2836 pupils blood and urine samples were obtained for measurement of T4, T3 and TSH and urinary iodine levels, by radioimmunoassay and digestion methods, respectively. Mean serum T4, T3 and TSH were 9.7±2.1 µg/dl, 159±62 ng/dl and 2.2±2.7 µU/ml. No significant difference was observed between girls and boys or schoolchildren in urban and rural regions. In all, 8 pupils had T4 > 12.5 µg/dl with T3 > 240 ng/dl; In which 7 had increased TBG and normal FT4I and FT3I. One child had thyrotoxicosis. In 3.9% TSH was > 5 µUlm! and 9 children had TSH > 10 µU/ml; In which 7 had normal FT4I and T4 (subclinical hypothyroidism). In 2 pupils increased TSH and decreased FT4I was present. Median urinary iodine excretion was 20.5 µg/dl, without significant difference between both sexes and urban or rural inhibitants. It is concluded that IDD prevention program has been effectively implemented in I.R. Iran. There is no evidence of increase in prevalence of thyroid derangementin schoolchildren of 8 to 10 years old.