The perinatal thyroid in iodine deficient regions: Risks of radioiodines -Hazards of stable iodine overload. A study in the newborn rat

Administration of large quantities of stable iodine is an effective means o f reducing the radiation burden on the thyroid in the event of a nuclear po wer-plant accident. Such administration may involve countries with low base line dietary iodine intake. It is questioned whether stable iodine overload is safe, and in particular, what are its effects in newborn infants? Iodin e-deficient newborn rats were submitted to a single acute administration of stable iodine (100 mug) on the second day of life. The effects on thyroid structure were studied, after 24 hr and after 7 days, using light microscop y. Compared to controls, the thyroids of animals submitted to stable iodine overload showed, 7 days after treatment, signs of acute toxicity including marked desquamation of epithelial cells and rupture of a large number of t hyroid follicles. Our findings in iodine deficient newborn rats suggest tha t stable iodine overload may have side effects during perinatal life. This prophylactic measure should, therefore, be accompanied by follow-up of thyr oid function. Thyroid hormones are critical for brain development, during t he first period of life.