distant metastases, the clinical prognoses for these individuals remains highly favorable. Although fourteen of these tumors were classified morphologically as malignant neoplasms (carcinomas), either occult or overt, it should be emphasized that the lay term "cancer," with its ominous implications, should not be applied to such clinically benign lesions, a point well noted by others (255,259). 2. Thyroidal Hypofunction Criteria used in defining biochemical thyroid function were developed from findings in the control and exposed Utirik populations presented in Table 6.* In the initial series, an upper limit of 3 UU TSH/ml serum was selected, Since baseline studies in 25 unexposed Marshallese who were clinically and biochemically euthyroid yielded a mean value of 2.0 wW/mi (SD = 0.73) with a range of 0.5 to 3.0 wW/ml. Serum TSH concentrations in this group after injec- tion with 500 ug of TRH averaged 11.5 uwW/ml (SD = 4.5) with a range of 4.7 to 20.0 wpU/ml. These results are similar to those obtained in other normal populations with respect to both basal TSH and TRH-induced TSH release (111,130,131). Table 6. Number of subjects with elevated serum TSH concentrations in control and exposed Marshallese populations (1975-1979). Initial Sub jects Tested once Control (unexposed Marshallese) Utirik exposed (thyroid dose <95 rads) Rongelap-Ailingnae exposed (No prior surgery) Series Single TSH Second Series Tested two >3 ww/ml or more times 115 ll (10%) 67 99 12 (122) 101 43 11 (26%) 36 Two TSH values >6 WU/ml 2 (3.04) 0 7 (19%) As shown in Table 6, only 10% of a control population of 115 had serum TSH concentrations >3 wU/ml. In the the Utirik population exposed to rela- tively low doses of radioiodine, 12% had single TSH values >3 UU/ml.. These re- Sults suggested that there was no difference between these two populations with respect to the prevalence of elevated serum TSH. In the exposed (but *Data from the exposed Utirik group were combined with the data from the unexposed group because that group showed no evidence of thyroid hypofunction associated with the low doses to their thyroids. - 70 -