Accordingly, (112,113). the TBGI parallels the free fraction of the thyroid hormones in serum. Normal values for serum T, range from 5.0 to 10.2 ug/dl in patients with normal concentrations of thyroxine-binding globulin (TBG), and the normal mean value for TSH is 2 w/ml with an upper limit of 4 wW/ml (110). For reasons to be explained, an upper limit of normal of 6 WU/ml was employed in some analyses of these data. In some of the exposed individuals, 500 Ug of TRH was given intravenously and TSH was measured 20 minutes later. Controls for these studies were nonexposed Marshallese living on either Rongelap or Utirik. Serum T. concentrations were measured in many of these subjects but are not vresented here because they are not pertinent to the present discussion. Fortunately some unused surplus samples of plasma, obtained for Ty measurements on the exposed Rongelap people as early as 1963, had been preserved in a frozen state. A retrospective study was done on these samples using the present assay techniques to measure T, and TSH levels in those that had been taken from individuals prior to surgery. C. Findings Except for thyroid nodularity, it is noteworthy that other thyroid dis- eases such as thyroiditis have been absent in this population. Also, evidence of thyroid dysfunction with hyper- or hypofunction was rarely seen except for hypofunction in the exposed Rongelap people, described below. 1. Thyroid Nodules (a) Clinical Characteristics Thyroid nodules were almost always asymptomatic, and patients were often totally unaware of their presence. In a few cases, nodules were tender, and in rare instances patients complained of sensations of neck fullness and/or discomfort on swallowing. Associated lymph-adenopathy was rare. None of the individuals with thyroid nodules showed clinical evidence of thyroid dysfunction, though serum hormone assays indicated subclinical hypofunction in some (see Section IX.C.2). As noted earlier, myxedema secondary to thyroid abla- tion developed in two exposed Rongelap bays eight years after radiation exposure, (b) Prevalence Table 1 summarizes the prevalence of thyroid abnormalities in the exposed and age-matched comparison populations. In Appendix IV, Table 1, individual cases with positive findings are listed along with estimated thyroid doses, age at detection of abnormality, diagnosis, and date and place of sur- gery. Since 1974, additional thyroid nodules have been detected in 5 exposed Rongelap people, 9 exposed Utirik people, and 14 unexposed people. Not listed in Table 1 of Appendix IV are a number of cases in which palpation of nodules was questionable, i.e., could not be confirmed definitely by a majority of examiners. As pointed out in Section IX.B, surgery was not performed in some cases because of old age, poor health, or other reasons. tients are being carefully followed. - 57 ~- All of these pa-