dards.22 No significant differences in the PBI levels were noted between the group that had been ex- posed to radiation and the unexposed group. Chemical studies of the sera revealed that the high PBI Jevels could be accounted for largely on the basisof high iodoprotein levels. Lack of recognition of this fact may have masked anincipient deficiency of the thyroid hormonein somecases during these early studies. Morerecently, after development of thyroid ab- normalities in the exposed Marshallese, it was possible to compare serum iodoprotein levels in cases with thyroid hypofunction with those in euthyroid populations. In Table 12 iodoprotein levels are compared for the Ailingnae, Utirik, Rongelap unexposed, and Rongelap higherexposure groups with and without thyroid abnormaiities. The highest iodoprotein values were noted in the Utirik population. The Rongelap unexposed population had higher values than the exposed population. The reasons for this are not apparent. Amongthe exposed population those with thyroid abnormalities showed about the same meanlevel as those with no thyroid abnormalities. Following thyroidectomy the iodoprotein levels were slightly Aww io | lower, but no difference was seen between those re- we ind inibe ‘erlese ian with subtotal and those with total thyroidectomy. These data indicate that radiation exposure may have resulted in a slight reduction of iodoprotein levels in the exposed population. Thyroidectomy, partial or complete, resulted in only a partial reduction in the iodoprotein levels; therefore, it appears that the major portion of iodoproteins are produced at extra-thyroidal sites. Urine iodine levels were in the normal rangein the Rongelap people, which indicates adequate intake in the diet, but the values werenot quite as high as expected in individuals living close to the sea and eating seafood. 132] uptake studies showed a depressed thyroidal iodine uptake rate and renal excretion rate in the Marshallese (unexposed people) compared with Americans. No explana- tion for these findings is available. These data are described in detail in the preceding report. Developmentof Thyroid Lesions Nine years after the accident an asymptomatic thyroid nodule was detected during routine annual physical examination in a 12-year-old exposed girl (#17), and the following year a 13-year-old (#621) and a 14-yr-old girl (#69), both exposed, were also found to have nodules of the gland.?3 Since then increasing numbers of thyroid abnormalities have appearedin the exposed Rongelap people. In 19 people nodularity of the gland has been the prominentfinding, and in 2 boys (#3. and 5) atrophy of the gland has developed. The nodules were usually multiple and non-tender and varied in consistency. Surgical exploration, described below, has been carried out in 18 of the 19 nodular thyroid glands. Benign adenomatous lesions were foundin al] these cases, and malignant lesions were also present in 3 of them. Oneadult with somewhatless significant nodularity of the thyroidis still under observation. Table 13 outlines the findings on individual cases. Appendix lists thyroid information on the entire exposed Rongelap population (including PBI, cholesterol, etc.). In view of the seriousness of these thyroid developments a panel of experts advised that the more heavily exposed Rongelap people be given supple- mental thyroid hormone. This treatment wasininstituted in September 1965. Table 14 lists the incidence of benign nodules (including atrophyof the gland) and malignant lesions and the estimated dose of radiation to the thyroid glands in the various populations under study. The highest incidence. of thyroid lesions (89.5%) has been noted in the heavily exposed Roneglap group who were <10 years of age at the time of the accident. The absence of lesions in people of the sameagein the lesser exposed and unexposed groupsis most notable. The incidence of thyroid lesions in those exposed as adults in the more heavily exposed group is considerably lower than in those exposed as children but is higher than in the adult population of the Utirik or unexposed groups. (Oneindividual was found to have an adenomatousthyroid lesion in the Ailingnae _ group.) Thefirst case of carcinoma ofthe thyroid was discovered in 1965 in a 41-year-old woman (#64) in the heavily exposed group, 11 years after exposure.?4.25 Ar that time the relationship of radiation exposure to appearance of this lesion was seriously questioned, although such lesions are rare in the Marshallese. However, in September 1969 surgical exploration ofthe thyroid on 5 Marshallese with palpable nodules revealed malignantlesions in 3 additional people. Two of these were women in the more heavily exposed Rongelap group,a 36- mes pare ae normal and that from 16 to 64% of the natives on Rongelap and 90% on Utirik showed values that were above the normal range by American stan- af! imme de calm A ap Se na a Fd Se LS Pl | [| Deo UutvbwwrvouHtseo | v 2