Evaluation of the impact of an iodine supplementation programme on severely iodine-deficient schoolchildren with hypothyroidism.

BACKGROUND: Northern rural areas of Tehran have been shown to have severe iodine deficiency in our previous studies. In 1989 the inhabitants of these villages received an injection of iodised oil, followed by iodised salt distribution in 1993. The aim of the present study was to evaluate the effect of the iodine supplementation on iodine-deficient schoolchildren with hypothyroidism in these villages.
METHODS: In total, 571 students aged 6-14 years were studied. Goitre was graded according to the World Health Organization classification. Serum concentrations of thyroid hormones (thyroxine (T4) and triiodothyronine (T3)) and thyroid-stimulating hormone (TSH) were determined using commercial kits, and urinary iodine was measured using a digestion method. The results were compared with data from our previous study in 1989.
RESULTS: Total goitre rate decreased by 42% in 1999 compared with that in 1989. A significant decrease in Grade 2 goitre concomitant with an increase in Grade 1 goitre was seen (P < 0.001). Values of the variables studied before (1989) and 10 years after iodine supplementation (1999) were: median urinary iodine excretion, 2.0 vs. 19.0 microg dl(-1) (P < 0.001); T4, 6.5 +/- 2.0 vs. 8.4 +/- 1.6 microg dl(-1) (P < 0.001); T3, 177 +/- 38.0 vs. 145 +/- 29.0 ng dl(-1) (P < 0.001); TSH, 10.8 +/- 15.1 vs. 1.8 +/- 0.8 microU ml(-1) (P < 0.001). No correlation was found between thyroid hormones and TSH on the one hand, and goitre and urinary iodine, on the other. Serum T4, T3 and TSH concentrations were within normal ranges in all schoolchildren in 1999.
CONCLUSION: This study showed that euthyroidism induced by administration of iodised oil in iodine-deficient schoolchildren with hypothyroidism is sustained following the consumption of iodised salt.