SESSION III 129 CONARD: Yes. We've done considerable work onthe different protein-binding levels of the different blood proteins. BUSTAD: On the basis of our work with radioiodine in animals and also a fairly extensive review of human data, J would not have predicted, nor can f find very many people that would predict, that you would see frank hypothyroidisin with 1400 rads from radioiodine and 175 r from gamma exposure. DUNILAM: Have you kept any animal ten years? BUSTAD: Yes. In fact, we have fed sheep radioiodine for II years MILLER: These were little sheep? every day of their life. BUSTAD: Yes, they were exposed in utero since their mothers were fed radioiodine. In the cases of the Marshallese children, their dose waa an acute one at a sensitive time, but since the calculated dose appears insulficient to cause hypothyroidism !'m wondering if there could have been two or three times the thyroid dose in some children. Maybe they drank more water or maybe a few children licked themselves and contaminated objects around them and realized significantly higher exposure, IL have difficulty getting three times as much, which I would say might be the minimum exposure from radioiodine which would result in frank hyperthyroidism. I would like some reaction to this. FREMONT-SMITH: Is this potentially a species difference? BUSTAD: I think generally the acute ablating dose for most animals is very nearly the samc. In an adult person it's reported to be about 30, 000 rads, which is similar to that we have observed in sheep. FREMONT-SMITH: Many other experiences with animals show that you do get species differences of various kinds and therefore prediction from several species of animals that you have used doesn't apply to humans. UPTON: Hewabout Sol Michaelson's work, George, in dogs? CASARETT: That work (Reference 27) beais out the fact that external radiation with x rays will cause hypotunction of thyroid, myxe-