57 a t I Y r r r ~—— 9 Thyroid lesions a (Rongelap + Utink) \ \ \ \ \ \ \ Nolesions (Rongelap) Af U.S. norma! Percent \ fy \ TGby RIA (ng/inl) 50 Nolesions (Uurik) Basal lof Shr 24 hr basal Pest TSH Shr 24hr ”* Figure 42. Effect of TSH administration on thyroglobulin <5 10 15 2 2 30 ng/ml Figure 41. Percentages of people in various groups having given levels of thyroglobulin (by RIA), 1973. and a high incidenceof parasitic infections. A preliminary examination of North Americans with abnormal leukocyte counts, however, did not show a correlation between leukocytosis and iodoprotein level. Further studies on this are indicated. The chemical nature of this iodoprotein is also unknown. By analogy with findings in various thyroid diseases,9? the iodoproteinis likely to be comprised mainly of iodoalbumin arising from the iodination of serum proteins. It is now recognized, however,that thyroglob- ulin (TG)is a minor componentof normal plasma. Ata reported concentration of 5.10.49 (S.E.M.) ng/ml (range <1.6 to 20.7) in normal North Americans,?4 and assuming an iodine contentof 0.5%, this would be equivalent to an iodoprotein iodinelevel of 2.60.25 ng/di. Althoughit seems unlikely, a pron, that circulating thyroglobulin in the Marshallese could be elevated enoughto give an iodoprotein level of 3 to 4 wg/dl (i-e., >500 pg TG/dl), the possibility was investigated by radioimmunoassay measurements (M. Izumi, J. Bauieu, AND J. Ropains, unpublished observations, 1974; see Figure 41). The assay could detect TG levels >5 ng/ml; levels >40 ng/ml were not quantitated. In the Rongelap and Utirik groups withoutthyroid lesions (47 and 25 subjects respectively), 3 80% of the values were within the U.S. range, and no correlation wasseen between elevated serum iodoprotein and abnormal TGlevels. A few members levels, 1973. Q, Persons with thyroid lesions (Rongelap plus Utirik); @, without lesions (Rongelap). of each group,including the U.S. normal group, had TG values >30 ng/ml, but the significance of this is uncertain. Of 24 subjects with elevated serum iodoprotein, only 1 had serum TG >30 ng/di. A striking finding (Figure 41) wasthat in the Rongelap plus Utirik group with thyroid lesions (36 people) almost 50% of the levels were <5 ng/ml, a much higher percentage thanin the other groups. Most of these people had had prior thyroid surgery or were athyreotic, and it is presumed that they hadinsufficient thyroidtissue for normal TG production. Furthermore, Ts suppression ther. apy may have contrifuted to the.low TG levels in the Rongelap people. “4: TG was also measured before and after TSH injection in 10 Ré&gelapslus Utirik subjects with thyroid lesions andin20 Rongelapese with none ry case,TSH resultedin a rise ain waseerreses difference } s OUpsi aeSe ‘, % Theunusually high level of ifjodopettern|in the Marshallesepeopleiis intriguing, and figrther stud- ies are.in progyess,With:F801.usediiithe&facer, in an step toent roe cr vw G. SORRELATION OF THYROIBigABNORMALITIES - * WITH RADIATION EXPOSURE Statistics on the incidence of thyroid abnormalities in people living on the Marshall Islands are *Miss R.F. Straub, BNL,is doing the chemical analyses.