3+ population. The findings also support the program of thyroxine replacement in the exposed Rongelap population to prevent both clinical hypothyroidism andtheassociatedrise in plasma TSH, which may be tumorigenic. wassignificantly lower (6.0== 1.8 wg/dl). Thefrequencydistribution calculations (see Table 29 and Figure 39) indicate that a substantial portion of the Utirik population has plasma Ty concentration <3 ywg/dl. Measurements of plasma tn- 4. Thyroid Function in the Utirik and tions in those patients with low Ty values. Plasma Unexposed Rongelap Groups iodothyronine (not shown) showedsimilar reduc- During the 1973 survey, Ts and TSH concen- 40 trations were measured in plasma from 109 unexposed Rongelap and 97 exposed Utirik subjects T e---a Utirik Rongelap group, 7.7 ug/dl, was the sameas in the United States, and, as in the United States, the plasma T, concentrations were skewed to the Group 109 Rongelap unexposed 97 Utirik exposed Subjects 4 T Subjects Plasma T,, ue/dl with value <5.0. with value >113 7.7420 6% 6% 6.0% 1.8* 32%** 6% 2.5 “Significantly different, p<(0.001. 5.0 Rongelap TBG-binding capacity n pg T,/dl TBG (RIA) elo yd7 Uli /My 40; TBG capacity ——— 1 1 Rongelap aap!! 4 I Exposed 12 All sera All sera* 25 22 Curik All sera All sera* 22 22 Unexposed mg/dl 12.5 lap unexposed groups having given thyroxinelevels, 1973. Thyroxine-Binding Globulin (TBG) Levels (Mean = 5.D.) in Serum, 1973 n 10.0 Figure 39. Percentages of people in Utirik and in Ronge- Table 30 Group 7.5 Plasma thyroxine (#g/ 100 mi) **6% had values <3.8. TBG by RIA t oa ow Plasma Thyroxine Concentrations (Mean = S.D.) in Utirik and Unexposed Rongelap Populations, March 1973 1 30 % oftotal population Table 29 ! @o—e Rongelap March 1973 (see Table 29). The mean Ty, in the unexposed upper range. In the Utirik group, the mean T, T 13 1.45240.54 14 21.54 69 1.64+0.95 1.3440.45 25° 21 23.14115 191+ 62 1.40+0.42 1.40+0.42 31 27) 189+ 78 16.4 43 1.8241.22 110 25.315.7 *Omitting sera with TBG >3 or TBG-binding capacity >30. Statistical comparisons revealed no significant difference ( p>0.05) between anyof the groups. 0 1 2 3 4 5 mg/dl O 10 0 30 ug T2/dl 40 30 Figure 40. Thyroxine-binding globulin levels in serum and TBG-binding capacity, 1973.