64 FALLOUT EFFECTS—MARSHALL ISLANDERS Since most of the carcinomas in the Marshallese were in the younger age group and were of the papillary type without distant metastasis, the clinical prognosis for these individuals is excellent (8,26,61). EFFECTIVENESS OF T, TREATMENT Evaluation of the prophylactic effectiveness of T, treatment in preventing developmentof thyroid nodules has been complicated by difficulties in maintaining a strict treatment regimen. Lack of compliance with the regimen has been reflected in some cases in elevated TSH levels, particularly in postsurgical cases, where the hormone replacementis essential to maintaining a euthyroid state. Three patients who had benign nodules removed have had recurrence of nodules. All three of these exhibited elevated TSH levels prior to recurrence, indicating inadequate compliance with treatment. The occurrence of thyroid nodules in the Rongelap-Ailingnae group appears to be slowing in the past few years (13), but this may be due to the smaller number of unaffected people living. (If one includes suggestive hypofunction, only 15 of 65 in this group now living have negative findings; in the Utirik ’ group 93 of 115 now living have negative findings.) Treatment with T, has undoubtedly been effective in enhancing growth and development in growth-retarded Rongelap children. A “catch-up” in growth has been sufficient that at maturity their statures were notstatistically different from those of their unexposed peers (55). DOSE-EFFECT RELATIONSHIPS The increase in thyroid abnormalities in the exposed Marshallese people is undoubtedly related to radiation exposure. There are no known goitrogens that might play a role, iodine intake is adequate in the Marshallese, and the increase in thyroid abnormalities was roughly correlated with estimated radiation doses to the thyroid. The association between radiation exposure and development of thyroid neoplasia has been well documented in animal studies (40-42), in children following therapeutic irradiation of the head and neck region (2,15,16,22,25,29,30,43, 45,50), and in survivors of the atomic bomb exposures to gamma and neutron radiation in Japan (5,47,60). Reports of neoplasia following I-131 therapy are morelimited (4,18), and it is generally conceded that such therapyis less tumorigenic thanx radiation (6,48,56). The few studies looking for thyroid abnormalities following diagnostic use of I-131 have had generally negative results, though many people have probably had thyroid exposure of several hundred rads from repeated procedures (24,31,32). Some people living in Nevada and Utah near Le *, an y £ oat the nuclear test site were exposed to somefallout in the early 1950s. Thyroid dose estimates range from 18 to 120 rads or more (49). (The variability is due