~J wa — &YVv —— Percent \ / U.S. normal é fy we wn neo mn No lesions (Rongelap) 30F TG by RIA (ng/ml WL 9 Thyroid lesions < (Rongeiap + Uurik) SS 50 Noiesions (Utirik) Lor Basal 8hr 24 hrbasal Post TSH Shr 2¢hr Figure 42. Effect of TSH administration on thyroglobulin levels, 1973. 5, Persons with thyroid lesions (Rong@lap plus Utirik); @, without lesions (Rongelap). Figure 41. Percentages of people in various groups having given levels of thyroglobulin (by RIA), 1973. and a high incidenceofparasitic infections. A pre- liminary examination of North Americans with abnormalleukocyte counts, however, did not show a correlation between leukocytosis and iodoprotein level. Further studies on this are indicated. The chemical natureof this iodoprotein is also unknown. By analogy with findings in various thyroid diseases,9? the iodoproteinis likely to be comprised mainly of todoalbumin arising from the iodination of serum proteins. It is now recognized. however, that thyroglobulin (TG) is a minor componentof normal plasma. At a reported concentration of 5.10.49 (S.E.M.) ng/ml (range <1.6 to 20.7) in normal North Americans,?? and assuming an iodine contentof 0.5%, this would be equivalent to an iodoprotein iodine level of 2.60.25 ng/dl. Althoughit seems unlikely, @ priort, that circulating thyroglobulin in the Marshallese could be elevated enoughto give an iodoprotein level of 3 to 4 ug/di (i.e., >500 pe TG/dl), the possibility was investigated by radioimmunoassay measurements (M. Izumi, J. BAuLieu, 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/dl. A striking finding (Figure 41) was that in the Rongelap plus Utirik group with thyroid lesions (36 people) almost 50% of fhe levels were <5 ng/ml, a much higher percentage than in the other groups. Most of these people had hadprior thyroid surgery or were athyreotic, andit is presumed that they had insufficient thyroid tissue for normal TG production. Furthermore, T4 suppression therapy may have i uted to the low TG levels in the Rongelap peo ERG TG wasalso measured before and after TSH injection in 10 Rangelap plus Utirik subjects with thyroid lesions an@in 20Rongelapese with none (Figure 42). In every case, TSH resulted in a rise in TGlevel, and there wasna,~epparent difference between. thetwa The unusually nigh tavaofidoprotein iin the Marshiilles Seopleiis intriguing, and furtherstudgress, with I used| asthe tracer, in AND J. Rossins, unpublished observations, 1974; see Figure 41). The assay could detect TG levels >5 ng/ml; levels >40 ng/mlwere not quantitated. In the Rongelap and Utirik groups without thyroid lesions (47 and 25 subjects respectively), > 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 G. cOATONOFTHYROID“ABNORMALITIES WIT RADIATION EXPOSURE Statistici on the incidence of thyroid abnormalities in people living on the Marshall Islands are *Miss R.F. Straub, BNL,is doingthe chemical analyses.