JAEA-SM-224/607 111 and the TSH response to TRH wasalso significantly increased, indicating the presence of impaired thyroid function. Characteristics of Marshallese with biochemical evidence of thyroid dysfunction In Table VII are presented the results of other studies in the four individuals with biochemical evidence of impaired thyroid function. At present, these are the only individuals who have fulfilled the criteria described in Table V, though several other subjects have shown at least one abnormal finding but have not had the required numberof tests to meet the established criteria. The age at exposure varied from 16 to 38 years and the estimated thyroid dose was thought in three or four to be less than 400 rads. Serum T, concentrationsin all four subjects are in the low normal range when considered in the light of their estimated serum Thyroxine-Binding Globulin (TBG). Subjects 74 and 71 have approximately normal serum TBG concentrations, whereas subjects 78 and 4 apparently have a modestly elevated serum TBG. In the last column of Table VII are shownresults of the TSH stimulation tests of these subjects performed in 1974. In all three, the serum T, response to TSH was impaired, suggesting decreased thyroid reserve. DISCUSSION rm SO1e3 cr An association of thyroid nodularity and cancer with prior radiation of the thyroid gland, particularly in younger patients, is well recognized and the association has recently been reviewed [11]. In addition, it has been recognized that radiation to the thyroid delivered in the course of treatment of patients with thyroid dysfunction is associated with hypothyroidism in a significant fraction of the patients (as high as 50%) at the higher dosage levels [12]. The lowest dosage considered in previousstudies of this type has been approximately 3400 rads estimated dose to the thyroid which was associated with a 6% probability of hypothyroidism within one year and a 13% probability in 13 years [13]. There are few data available in the literature relative to the possibility of hypothyroidism following '3I dosages ofless than 2500 rads. Preliminary results of Hamilton and Thompkins indicated that eight of 443 subjects (1.8%) subsequently became hypothyroid after diagnostic }*"I tests at less than 16 years [13]. A summary of these preliminary data has been presented. None of 146 subjects with an estimated thyroid absorbed dose of 30 rads developed hypothyroidism, but three of 146 subjects receiving 31 to 80 rads estimated thyroid dose had this condition [14]. Of 151 subjects with an estimated dose range of 81—1900 rads, five hypothyroid patients were found with an incidence of hypothyroidism of 0.23% yearly.