35 TSH concentrations were normal. For this reason, TBG-binding capacities were determined in a numberof subjects with abnormal Ty, values. ' TBG analyses were done on sera from 56 sub- jects (25 Rongelap and 31 Utirik) selected as representative of three groups: people with low, normal, or high plasma T4 concentrations. Two methods were used: TBG was measured by radioimmunoassay (M.C. Gershengorn and J. Robbins. unpublished observations, 1974) and TBG-binding capacity bv reverse-flow paper electrophoresis. The results were comparable since the mean ratio of TBG-binding capacity (ug Ty/dl) to TBG (mg/dl) was 13,9. On the basis of one mole T4 Table 31 Total and Free Thyroxine, Thyroxine-Binding Globulin, and Thyrotropin Levels in Marshallese Subject No. TBG,yg/dl Ta, pe/dl Subjects with TBG-bindcapacity <14 pg T./dl 827 7.6 (1.06) * 5.1 917 7.0 (1.20) 4.4 981 8.0 (0.69) 4.4 2115 7.7 4.4 2126 9.1 4.9 44 7.0 4.0 174 7.1 4.1 2193 11.1 (1.03) 4.8 2290 13.7 3.2 2248 11.9 (0.94) 3.8 2185 4.6 Mean 9,02 4,34 §.D. 2.39 +0.543 Subjects with TBG-bindingcapacity 14 to 26 ug Ts/di 850 2135 2137 2212 2206 2182 2218 2221 2232 2257 2168 2136 2230 14.0 (1.04) 15.5 19.9 (1.37) 20.1 17.7 14.4 14.3 15.6 16.2 (1.54) 17.3 14.1 15.5 (1.06) 21.9 (1.28) Mean S.D. 4.6 6.1 9.2 5.0 7.4 5.0 3.0 4.8 4.8 8.8 4.2 7.7 6.1 Mean $.D. TSH, pU/mi 3.37 3.53 3.24 3.21 3.20 3.76 4,23 3.23 3.12 2.94 2.80 3.33 +0.40 1.72 1.35 1.43 Lal 1.37 1.50 1.73 1.55 0.998 1,12 1.29 144 0.230 ~ 3.1 2.3 <1.0 <3.0 52.5 <1.0 4.2 3.6 <2.5 3.08 2.94 2.90 1.84 2.97 2.92 3.04 2.68 2.42 2.94 2.72 215 1.45 1.42 1.79 2.67 0.92 2.05 1.46 0.912 1,29 1.16 2°57 1.14 1.66 0.885 16.63 5.9 2.60 1.87 +0.503 37.0 (1.52) 35.7 56.1 (4.56) 47.6 (3.92) 32.8 51.8 43.5 +9.62 *TBG by RIA, mg/ml. OGs'o2 Free T,, ng/dl 2.58 Subjects with TBG-binding capacity >26 ue T,/dl 2138 2229 aol 911 2217 2256 DFT, x 10¢# 9.0 5.9 12.9 13.6 7.0 18.2 11.05 4.63 2.01 1.53 1.22 0.872 1.88 0.991 1.42 0.468 , 2.6 21 2.6 <25 2.8 2.5 3.6 <5.0 6.0 2.0 2.5 2.1 4.9 1353 +0.597 L.81 0.903 1.54 1.19 1.32 1.80 1.43 *+0.358 24 10.8 2.1 2.7 44