27 Table 15 ad NO. OF CASES Kinetic Studies With"4 Group A..* A,,** Marshallese U.S. normals 0.72 1.0 0.97 2.0 Theoretical ~ = No. uptake o,,f case 42% 33% 0.08 - 21 mo *Fraction of extrathyroidal iodide transferred to the thyroid per day. **Fraction of extrathyroidal iodide excreted in the urine 8 io PROTEIN « SOUND IODINE, wq % 12 Figure 21. creased the background slightly. Mathematical analysis® of these data was done on an IBM 7094 computerwith the program of Bermanet al.** No experimental correction was madefor extrathyroidal radioactivity “seen” by the counter, since the computer program adjusted the readings over the neck for this factor. A least-squares best fit, as- suming e?.ponential thyroid uptake andrenal excretion ofiodide, produced a “best” value for this factor, termed o;,. Theresults of the studies with 'S?77 are shownin Table 15, where they are comparedwith values obtained from normal individuals #etiding in the United States. It can be seen that the rate of thyroid uptake andtherate of urinary excretion are both decreased. Since they are decreased more or less proportionately, the calculated asymptotic uptake is normal or slightly elevated. One may use these data plus the urine iodide values to cale#ate the average daily secretion of thyroid hormone, assuming steady stateegnditions, using the formula EU °=T=U where S = amount ofiodine secretedby the thyroid- (ug/day), U = fractional thyroid uptake of iodine, and. F£ = urinary iodine (pe/day). With E= 105 yg/day and U=0.42,the value for § is calculated to be 76 pug iodine/day. This valueis *We are indebted to Dr. Mones Berman, National Institutes of Health, Bethesda, for this analysis. per day. tValue derived by the computer for the |fraction of extrathyroidal iodide “seen” by the counted: somewhat higherthan similar ones calculated for other groups but is not extraordinarily hig!. ‘7 Serum Cholesterol. Serum cholesterol deter a.- nations on mostof the exposéd and an equal num- ber 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 !7% below the levels in the unexposed group,the difference is not quite significant at the 5% level. Individual values were not indicative of thyroid disease. Discussion of Previous Thyroid Studies. Until the recent development of 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 anelevation of thyroxine-bindin-. proteins in serum which, asin the congenitas 2seva‘tion of thyroxine-binding globulin described by _ Beierwaltes and Rébbins,”* causes an increfte in the gsrum PBI withous hyperthyroidism. The levels of the TBG in the Marshallese serum measured by Rebbins, however, were within norma! limits. The discrepancy between PBI and BEI suggested the-prespnce of an iodoprotein in serum. The chromatographyof serum iodine showing an iodgprotein level in the Rongelappeople of 2.2 pg% (and higherfa the Utirikpeople) seemsto implicaté the sodoprotein as the cause for the ele- vated PBI. 7 ~ No adequatedataare available’ on ‘the calorigenic potency ofaerum iodoproteins, but there are some results which show that most of the iodinated amino acidsin this protein are monoiodotyrosine and diiodotyrosine.***” These iodoamino acids are