334 CONARD er al, DISCUSSION ; - As a result of the exoosure of the Marshallese people to radioactive Saiiout 15 years age the only late findings of significance have been the development of thyroid abnormalities with resulting retardation of growth and development in the more heavily exposed children. The lack of development of nodules in the unexposed and lesser exposed populations in the same age range clearly indicates the etiological relationship of the lesions to radiation. ‘The higher incidence of nodules in the children than in adults is probably related to the larger dose of radiation re- ceived by their smaller glands. - The high incidence of these lesions in nee eee enti 5,6) a this population is perhans a little surprising in view of the consideration of the dose and dose rate from radiofodine exposure in a fallout situation. The fact that a large part of the dose was from short-lived radio- iodines with fast dose rate may have been important. The development of these thyroid abnormalities is consistent with reports in the literature on many animai studies and some human studies.77,8] Sheline et al. [9' Z have reported the development of nodules in follow-up studies of children for hyperthyroidism with radioiodine and more recently Pincus et al. 510? have reported a high incidence of nodules in children who had been treated with x-radiacion of the neck in infancy. rr The insidious onset ot thyrvid hypofunction and retardation of grewt in the Marshallese children was probably associated with the slow loss of functioning thyroid cells through lack of replacement due fo radiation impairment of cellular replication. One can speculate that less injured cells in the thyroid probably responded co the increased TSH simulation and che picture of concomitant atrophy and hyperplasia "9 + tome se resulted in gross nodule formation, In the 2 cases with complece thyroid atrophy, however, there must have been sufficient radiation damage to prevent appreciable responses to TSH stimulation, No dvoube there is increased risk of cancer of the thyroid in the Marshallese children and it is perhaps chance that no such malignancies have vet heen discovered. The Literature is replete with many retrospective as well ac prosnective studies which show the late development of cancer of the thyroid ic children that had been treated with cervical irradiatien during infaney and varly childhood.[ 11-13} Mowevur, there is scant evidence as yet for the development of cancer of the thyroid following radioiodine treatment. Increased prevalence of cancer of the thyroid has been reported {n adults exposed to the atomic bomb in Hiroshima !14] and other cypes of radiation.{/15: Ic is of course not possible to prove the causal relation- ship of irradiation in the case of cancer of che thyroid in the exposed women reported here, but in view of low incidence of such lesions in the Marshallese, this possibility must be seriousiv considered. "le 743 ” PLS It is not «known whether treatment with thyroid hormone will reduce the risk of cancer of the thyroid in the human being. However, such suppression has been teported to prevent the ceveicpment ef thyroid nodules in rats.£16; It is hoped that the hormone treatment being given the Marshallese miy suppress such neoplasia from radiation. REFERENCES os pee aod Load Pie at ee [1] ‘CONARD, R.A., HICKING, A., Medical Findings in Marshallese people exposed to fallout radiation: (1965) 457. results from ten-year study, JAMA 192 “45 . [16