Table 7. Results of serum analyses in exposed Marshallese subjects with at least two TSH assays >6 W/mi (1980). Subject No. & sex Date of sample Serum TSH ( WU/m1) 3M 5M 4m 1977 1963 1972 1974 1969 1979 1974 1979 1974 69 500 6.0 7.0 6.3 6.5 6.3 8.3 10 2.5 0.5 7.3 5.4 4.4 4.9 7.1 8.0 4.2 1979 1980 8.8 7.3 7.6 5.1 16M 34F 71F 1977 1977 78F 32M 7 6.6 Normal control range: 0-6.0 Serum Ty, (te /dl) 5.2 6.1 5.0-10.2 TBGI (units) Age at exposure Estimated thyroid dose (rads) 0.95 0.71 -0.82 0.89 0.91 -0.74 -- 1 1 38 1150 1150 335 39 135 45 335 27 335 37 335 3 1050 0.98 0.82 0.68 0.89 0.85-1.10 observation of elevated TSH in the individuals listed in Table 7 cannot be attributed to age alone. No. 4 and No. 78 were among those in whom TSH stimu- lation tests had been performed earlier. Both had Ty, increments of <1 Hg/dl 24 hours following 10 units TSH administration, a clearly subnormal response showing that these thyroids had no capacity to respond to increased demand. To evaluate the pituitary/thyroid axis more completely, TRH studies were done in some individuals. Results on subjects No. 4, 71, and 78 are given in Figure 5. Data from subject No. 74, discussed below, are also shown. This patient had surgery subsequent to the test and is therefore categorized sepa- rately (Table 8). Subjects No. 4, 71, and 78 all were hyperresponsive to TRH stimulation, with serum TSH values at 20 min >22 WU/ml, which is the 97.5% confidence interval for mean normal responses in the Marshallese. | I 40} s 74 Sr rat w J 20; a | /* oh L |} 4 a co co fo cy C1 BASAL AFTER TRH Figure 5. Basal plasma TSH and TRH- stimulated TSH in euthyroid Marshallese and in four exposed subjects with biochemical evidence of impaired thyroid function. Plasma was obtained 20 min after infusion of 500 Ug TRH. The upper limits of the normal range are indicated by the shaded bars. —~72-