25 roid then resulted in a substantially larger dose. The total estimated dose from the various iodine isotopesto the child’s gland was about 1000 rads, with a range of 700 to 1400. The glands received an additional 175 rads from external gamma radiation. Details of these calculations have been given by James and Ng and are presented in Appendix 2. Although the skin overlying the thyroid gland was frequently the site of “beta burns” as shown in Figure 20, the deposit of radioactive materials in this area probably did notaddsignificantly to the thyroid dose, since most of the beta irradiations were too weak to have penetrated to the depth of the gland. Previous Thyroid Studies Figure 20. “Beta burns” of neck (subject No. 39, March 1954), The area over the thyroid was a frequent site of thyroid enlargement seen in an unexposed woman. burns. amination of the thyroid and a variety of tests of care has been taken to ensure that glassware and syringes were not contaminated with iodine. This can be seen by the fact that the total! iodine is not markedly greater than the PBI and by the normal values for PBI obtained in 1964 on members ofthe It has not been possible to perform basal metabolism rate determinations, but careful physical ex- thyroid function have been performed during the previous surveys. Protein-Bound lodine.** The serum proteinbound iodine has been determined by the methods of Foss et al.?* at Brookhaven National Laboratory, the Boston Medical Laboratories, and Bio-Science Laboratories, Van Nuys, California. In addition, estimation of the butanol-extractable iodine of serum was done at Bio-Science Laboratories, and also column chromatographyof the serum iodine by a modification of the method of Galton and Pitt-Rivers.In several instances the capacity of thyroxine-binding alpha globulin (TBG) was measured at NIH by a method described previously." The results of analyses for iodine in serum are shown in Table 14. (See Appendix 3 for complete protein-bound iodine data.) It is apparent that on several occasions and with several different methods the average serum protein-boundiodine in the inhabitants of both Rongelap and Utirik is higher than normal, and that from 16 to 64% of the natives on Rongelap and 90% on Utirik show values that are above the normal range by American standards. No significant differences in the PBI levels have been noted between the group that had been exposed to radiation and the unexposed group. The first results showing an elevated PBI were obtained in 1958, and since that time medical team, whose blood was obtained at the same time and underthe same conditions as that of the natives. The elevation in PBI could be due to a general increase in serum PBI in all the Rongelap popu.a.ion, or it could be dueto the occurrence of some genetic difference, so that a substantial fraction of the population shows abnormally high PBIs and the remainderof the population is normal. In the first case, a plot of the level of PBI versus frequency of occurrenceat thatlevel would show a normaldistribution, except that the whole curve would be displaced about 2 ug% up- wards. In the second case, the distribution curve would be bimodal, and a family tree would show familial clustering, the precise type depending on the manner of inheritance. Figure 21, a distribution curve of PBI level versus incidence at that level, shows no evidence for a bimodal distribu- tion. The low numberof PBI values between 7.75 and 8.0 ng% seemsto be due tostatistical fluctu- ation because of the small numbers of cases. Furthermore, the elevated values (defined as those above 8.0 ng%) did not show a familial pattern of distribution. It appears, therefore, that the eleva- 4 Until 1963 no thyroid abnormality was detected in either the exposed or the comparison population, except for one case of asymptomatic diffuse