Table 15 NO. OF CASES Kinetic Studies With **71 PROTEIN - BOUND IODINE, #9 % Figure 21. creased the backgroundslightly. Mathematical analysis* of these data was done on an IBM 7094 computerwith the program of Bermanetal.** No Group An* Agi ** Marshallese U.S. normals 0.72 1.0 0.97 2.0 Theoretical No. uptake o,f cases 42% 33% 0.08 - 21 - *Fraction of extrathyroidal iodide transferred to the thyroid per day. **Fraction of extrathyroidal iodide excreted in the urine per day. tValue derived by the computer for the fraction of extrathyroidal iodide ‘‘seen” by the counter. somewhathigherthan similar ones calculated for other groupsbut is not extraordinarily high.**-*’ Serum Cholesterol. Serum cholesterol determi- the computer program adjusted the readings over the neck for this factor. A least-squaresbestfit, as- nations on most of the exposed and an equal number of the unexposed population were carried out in 1957 and 1959. The results are tabulated in Appendix 5. Although the cholesterol levels in the exposed group are about 17% belowthelevels in cretion of iodide, produced a “best” value for this significant at the 5% level. Individual values were experimental correction was madefor extrathyroidal radioactivity ‘‘seen” by the counter, since suming exponential thyroid uptake and renal exfactor, termed 63). Theresults of the studies with '**] are shown in Table 15, where they are compared with values obtained from normalindividuals residing in the United States. It can be seen that the rate of thy- roid uptake andtherate of urinary excretion are both decreased. Since they are decreased more or less proportionately, the calculated asymptotic up- take is normalorslightly elevated. One may use these data plus the urine iodide values to calculate the averagedaily secretion of thyroid hormone, assumingsteadystate conditions, using the formula EU S=Ty where S = amountofiodine secreted by the thyroid (ug/day), U = fractional thyroid uptakeofiodine, and £ = urinary iodine (g/day). With £=105 pg/day and U=0.42, the valuefor § is calculated to be 76 wg iodine/day. This valueis *We are indebted to Dr. Mones Berman. National Institutes of Health, Bethesda, for this analvsis. the unexposed group, the difference is not quite not indicative of thyroid disease. Discussion of Previous Thyroid Studies. Until the recent developmentof hypothyroidism in two boys, it had been the concensusofall physicians who examined these people that they were euthy- roid. A conceivable explanation for the high PBI could be an elevation of thyroxine-binding pro- teins in serum which, as in the congenitalelevation of thyroxine-binding globulin described by Beierwaltes and Robbins,** causes an increase in the serum PBI without hyperthyroidism. The levels of the TBG in the Marshallese serum mea- sured by Robbins, however, were within normal limits. The discrepancy between PBI and BEIsuggested the presence of an iodoprotein in serum. The chromatography of serum iodine showing an iodoprotein level in the Rongelap people of 2.2 pe% (and higherin the Utirik people) seemsto implicate the iodoprotein as the cause for the elevated PBI. No adequate dataare available on thecalorigenic potency of serum iodoproteins, but there are some results which show that mostof the iodinated amino acids in this protein are monoiodotyrosine and duodotyrosine.**-*° These iodoamino acids are