Reevaluation of the newborn thyroid dose from radioiodines.

The basis for the current thyroid absorbed dose estimates for radioiodines has been examined. The values for the newborn thyroid dose were found to underestimate the dose by a factor of 3. This underestimation of the dose was caused by the assumption that the biokinetic distribution of iodine is the same for the newborn and the adult. Increased thyroid uptake by the newborn requires that higher cumulated activities be incorporated into the dose determinations for the newborn.