ence of antithyrogiobulin antibodies in unexposed versus exposed groups ( Morimoto etal.. 1987). In addition. no difference in the prevalence of chronic thyroiditis was found in children considered exposed or unexposed to radioacuve fallout in Utah and Nevada ( Rallison etal.. 1974). Notably, in that study the prevalence of elevated titers of antithyroglobulin antibodiesin children with “normal” thyroids was 4.8"%. Hypothvroidism is commonin aging populations, and in the Framingham Heart Study a clearly elevated thyrotropin (TSH) level was found in 4.4% of persons older than 60 years (Sawin et al.. 1985a). The prevalence of antimicrosomalantibodies also increases with age: two-thirds of elderly persons with evidence of thyroid hypofunction hadsignificant levels of antimicrosomal! antibodies (Sawin et al.. 1985b). The Marshallese data Suggest that autoimmune thyroid disease is not commonin that population. regardless of a history of radiation exposure. NONCANCEROUS THYROID MORBIDITY IN EXPOSED MARSHALLESE The late somatic effects of exposureto ioniz- ing radiation have been equated with cancer induction, the ultimate measureof those effects being expressed in mortality. Since cancer mor- tality from radiation exposure is low when comparedto naturally occurring cancer mortal- ity it is not surprising that there is no observed increase in mortality among the radiationexposed Marshallese. Nevertheless. much attention has been addressed to their cancerrisk. On the other hand, limited attention has been given to morbidity from nonmalignant disease, principally of the thyroid, as a late consequence of radiation exposure, and yet these lesions have been of great clinical importance(Table 5). A. Thyroid surgery: Twenty-six (30 %) of the Rongelap group and eighteen (11%) of the Utirik group have had surgery for thyroid nodules that were ultimately found to be benign. The types of thyroid nodules found in the exposed population since 1963 can be grouped into cancers, adenomas. and ade- nomatousnodules. Cancers and adenomas are neoplasms. Adenomatous nodules. which, like adenomas, are benign, are not properly categorized as neoplasms. Histologically, they are hyperplastic lesions. In the exposed population both benign nodules and thyroid hypofunction display a similar correlation with radiation dose (Fig. 5), and, in contrast to thyroid cancer, adenomatous nodules have been very common(see Table 3). Adenomatous nodules are rarely of clinical significance, because they do not evolve into carcinoma, Surgery is necessary only to TABLE 5: LATE THYROID MORBIDITY UNRELATED TO DIAGNOSIS AND TREATMENT OF THYROID CANCER IN 253 RADIATION-EXPOSED MARSHALLESE. Morbid event Number of cases Thyroid surgery for benign lesions Hypothyroidism. radiogenic Pituitary tumor* Total morbid events * Possible association (Adams et al.. 1984). JO0u TTS —_— Recurrent laryngeal nerve palsy is Hypoparathyroidism, postsurgical bo Hypothyroidism, postsurgical 85