W. H. ADAMS: LATE MEDICAL CONSEQUENCES OF EXPOSURE TO RADIOACTIVE body radiation is now thought by manyto reflect the frequency of the different types of cancer normally occurring in a population. There is no known marker for radiation-induced cancer. Noncancerous Thyroid Morbidity The late somatic effects of exposure to ionizing radiation have been equated with cancer induction, the ultimate measure of those effects being expressed in mortality. Since cancer Table 8 Late thyroid morbidity unrelated to diagnosis and treatment of thyroid cancer in 253 radiation-exposed Marshallese Morbid event . Numberof cases Thyroid surgery for benign lesions 44 Hypothyroidism, radiogenic Hypothyroidism, postsurgical 15 21 Hypoparathyroidism, postsurgical Recurrent laryngeal nerve palsy 2 1 Pituitary tumor* 2 Total morbid events 84 moftality from radiation exposure is low when comparedto naturally occurring cancer mortality,it is not surprising that there is no observed increase in mortality among the radiation-exposed Marshallese. Nevertheless, much attention has been addressed to their cancer risk. 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 8). Thyroid Surgery Thirty percent of the Rongelap group and 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 adenomatous nodules. Cancers and adenomasare neoplasms. Adenomatous nodules, like adenomas, are benign, and are not properly categorized as neoplasms. Histologically, they are hyperplastic lesions. In the exposed 286