Effects of iodine repletion on thyroid morphology in iodine and or selenium deficient rat term fetuses, pups and mothers

It has been suggested that selenium deficiency aggravates the iodine-induce d thyroid inflammation and necrosis in iodine-deficient Wistar rats and pos sibly in man. Studies were carried out to determine whether large amounts o f iodine given to iodine-deficient pregnant Sprague-Dawley rats with or wit hout selenium deficiency would induce inflammation and necrosis in their te rm fetal thyroids. Iodine deficiency was induced in the dams by a low iodin e diet or perchlorate in the drinking water and iodine excess was achieved by iodinated drinking water during pregnancy or daily subcutaneous injectio ns of iodine from days 20 to 22 of pregnancy, 1 day after perchlorate was d iscontinued. Studies were also carried out in 30-day-old pups whose nursing mothers were iodine-deficient (perchlorate) with or without selenium defic iency from conception onward. The administration of iodine restored the mor phologic changes in the thyroid induced by iodine deficiency, irrespective of selenium status, toward normal without inflammatory changes or necrosis. Possible explanations for these unexpected findings are discussed. (C) Soc iete francaise de biochimie et biologie moleculaire/ Elsevier, Paris.