The dose of radiation to the thyroid, the average thyroid weights of [the mother rats, and the average thyroid weight of the offspring by litters is shown —in the attached Figure 12. Tt is condluded that animals born of mothers with some thyroid damage do not display thyroid hypertrophy at 100 days of life, which is canparable to adblescence in man. At the present time, the autoradiographs and histologic interpreta ion of thyroids of the mother rats have not been evaluated since they remain in preparatian. Since the time that the question was raised concerning the significange of adolescent goiter in the children of radiated Marshallese people, a furthe# recent survey made on Likiep Atoll (remote to the area of fallout) has revealed alfew mild adolescent goiters in native Marshallese. This excludes a few other goitegs appearing nndd 1311 om the All during the life of this contract, the principal investigatur and have been concerned with the morphologic changes that are produced in by radioiodine. The devastating effect of a large dose of radioiodine wi His associates did tissue the complete loss of thyroid epithelium and replacement by connective tissue is well kn@m. the hyperplasia of the thyroid of Graves’ disease is subjected to radiciod the hyperplastic picture of papillary projections into thyroid follicles a more simple follicular picture. With a large dose of radiation, the fo distorted and the general architectural pattern of the thyroid is markedly When radiation, changed to es are tered 2D the extent that there may be only scattered surviving epithelium cells in cbhnnective tissue. These changes are we}}, known and easily recognized, but the more shbtle changes produced by smaller doses of IT are difficult to identify with certainty. Various workers have described a variety of changes that indicate subthe radiation effect. In trying to identify these subtle changes, we have stressed the récogniticn of the large bizarre nuclear forms containing excessive amounts of chromatih. Other workers have placed more emphasis on lymphocytic infiltration, plasma cells land increased amounts of comnective tissue. Unfortunately, changes similar to fhese my occur in thyroids which have not been subjected to radiation. Lymphocytic iltration is a common finding in thyroids of patients with Graves' disease. The presence of } connective tissue may represent past influences on the thyroid such as necrgsis, repeated hyperplasia and involution and varying degrees of nodularity. Obj¢ctions may be made to using the large bizarre nuclear forms as a means of identifying gadiation because somewhat similar changes may occur in the margins of areas that are|starting to undergo necrosis. From the considerable opgymence studying pathologic charges in | tissues of patients treated with 199] and I and the extensive experience with animal thyroids that are subjected to various degrees of radiation, we have come td the | conclusion that a careful consideration of the bizarre nuclear forms is the best clue to the more subtle degrees of radiation effect caused by radioiodine.