LATE EFFECTS OF RADIOACTIVE IODINE IN FALLOUT Weknowthatit takes several thousand rads of local radiation to bone to produce retardation of bone growth. Ourestimates of the dose to the bones from the absorption of internal isotopes- in the children amounted to only 3 to 4 rads, and it was believed this dose was far too low to be of any signifiance. In searching for an answer, we carried out studies on weanling rats, | giving them sublethal doses of radiation and shielding one leg (14). We found that the tibial growth was retarded in both legs, including the shielded leg, the latter repre- senting an indirect effect of radiation. We carried out further pair feeding studies and measured the growth rate of the tibia in unexposed rats who were fed the samereduced amount of food as ingested by the irradiated animals. We found that there was a radiation-induced reduction in food consumption that apparently resulted in nutritionally induced retarded bone growth. However, in regard to the Mar- shallese, although some weight loss was noted in the children, it is not believed that a nutritional effect was of great significance in contributing to bone growth retardation. With the recent development of thyroid abnormalities in the Rongelap children, we have fairly strong evidence for the correla- tion of such abnormalities with growth retardation. The most striking correlation occurred in the case of the two boys with growth retardation who had bone ages of 3 and 5 years at the chronological age of 12. Their PBIs dropped to less than 2 yg/ 100 ml, they showed coarse facies, dry skin, sluggish achilles reflex returns, and appear- ance of bony dysgenesis in one case. As will be shown later, their TSH values rose to very high levels, which indicated a primary type of hypothyroidism. Figure 8 shows these stunted boys. The earlier lack of cor- relation of growth retardation and thyroid deficiency may havé been dueto the falsely high PBIs. The crucial test of all this is the response of these children to thyroid 1229 hormone treatment. At this point I think the results are encouraging. Westill have to evaluate the data on manychildren, but it does look as though there is an effect. The two most retarded boys have shown definite spurts in bone age andstature. Dr. Rall and I have just returned from the Marshall Islands, and we fee] that the hormone therapy is also causing some regression in the four cases that still have nodules. One nodule in a 40-year-old man has disappeared. These cases will be reevaluated for surgery on the next survey in March 1967. We have hopes that the hormone treatment will prevent further development of nodules. Whether it will have any effect on the carcinogenic action of radiation remains to be seen. Tuyrow Funcrion in MARSHALL ISLANDERS Dr. Rossins: I shall carry on the discussion myself now and bring upfirst some of the studies that were done on thyroid func- tion in the Marshallese individuals. A complete report of the measurements up until 1966 has been published by Drs. Rall and Conard (12). As Dr. Conard said, in the earlier days of the studies attention was given to the problem of thyroid dysfunction. Although this was looked for quite actively, none was found. Table 5 shows one of the reasons for this, and that is the finding to which healluded, that the Marshallese people have a higher average PBI and a higher range of PBI than do people living in our part of the world. Table 5 presents the results of studies carried out at various times over the years. When the first values for serum PBI came out high, the question of contamination was brought up. In 1964 the members of the medical team had their blood drawn under exactly the same conditions, and their PBI levels fell in the range that we have come to expect for the PBI in North America. The Marshallese, however, continued to show an elevated PBI with a high mean ParapetTe Volume 66, No. 6 June 1967