~i on 50 ¥G by RIA (ng/ml) Thyroid iesions (Rongelap + Uunk) Nolesions (Rongelap) \ A4 U\S. normal Percent 30r Basal <5 10 1 2 ng, ml 2 30 3 0< 8 hr 24 hr basal Post TSH 8hr 2+ hr Figure 42. Effect of TSH administration on thyroglobulin levels, 1973. =, Persons with thyroid lesions (Rong@lap plus Uurik); @, without lesions (Rongelap). Figure 41. Percentages of people in various groups having given levels of thyroglobulin (by RIA), 1973. and a high incidenceof parasitic infections. A pre- liminary examination of North Americans with abnormalleukocyte counts, however, did not show a correlation between leukocytosis and iodoprotein level. Furtiter studies on this are indicated. The chemical natureof this iodoproteinis 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 thyroglobulin (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,93 and assuming an iodine contentof 0.5%, this would be equivalent to an iodoprotein iodine level of 2.60.25 ng/dl. Although it seems unlikely, a preort, that circulating thyroglobulin in the Marshallese could be elevated enoughto give an iodoprotein level of 3 to 4 wg/dil(i.e., >500 ue TG/d)), the possibility was investigated by radioim- munoassay measurements (M. Izumi, J. Bautieu, AND J. Rossins, unpublished observations, 1974; see Figure 41).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 without thyroid lesions (47 and 25 subjects respectively), 2 80% of the values were within the U.S. range, and no correlation was seen between elevated serum iodoprotein and abnormal TGlevels. A few members 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 | had serum TG >30 ng/dl. A striking finding (Figure 41) was that in the Rongelap plus Utirik group with thyroid lesions (36 people) almost 50% of the levels were <5 ng/ml, a much higher percentage than in the other groups. Most of these people had had prior thyroid surgery or were athyreotic, and it is presumed that they hadinsufficient thyroid tissue for normal TGproduction. Furthermore, T4 suppression therapy may haveionato the low TG levels in the Rongelap peop 3 ES TG was also measured beforeandafter TSH injection in 10 Rongelapplus Utirik subjects with thyroidlesions an@in 20Rongelapese with none (Figure 42). In every case, TSH resulted in a mse in TG level, and there was+NO,agpparent difference between thetwo’ The unusualfy- nigh level ofiaidoprotein ii n the Marshall ies arein P ypleis intriguing, and further studb, with 129] used asthe tracer, in an attesnpe tescetghty = the protege 3=" ao + Be ~» = — G. CORSELATION ¢OF THYROID"ABNORMALITIES <>WITHRADIATION EXPOSURE Statisied on the incidence of thyroid abnormalities in people living on the Marshall Islands are *Miss R.F. Straub, BNL, is doing’the chemicalanalvses.