2 genie effect in rats anddogs is equal on a rad basis dibabe thyroid dose from abserprion af radioiodines in tiHout, considers the shorter-lved isotopes to be 4 times as energetic as 88) The more cnergene bets radiation with a higher dose rate and longer range gives anoruniter tissue distribution of radiae tien than is produced by EL Phas aiglit explain whythe ticidence of thyroid lesions in the children fae receiving 1000 rads falls an a line comresponding to babe 1000 rads of x-radiation (Figure 44). ar i aight indicate that the radiotodiae exposure was about TO ines as ctfecrive as /Y PE alone would have been ieee Chale Thus the twe boys with ateaply of the thyraid: may have bad doses te the wland com, parable with 40000 te GU00 rads ar morc of siracliations,. teal were . ’ hee bade . sant woos anal u ‘» fe 1 Petal age, an weeks . [ . Abogado ‘ u. Hi Ia da ededn enna lo that of x rays. Walinder et al. have reported similar findings. °4-6Dunning. ©jn estimating ee Gaal * Ma lars Nahaala Figure 18. ‘Vivnsdal uptake of MU per granny versus age. (From Fans et ale) 3. The Development of Thyroid Abnormalities From In Utero Exposure The development of thyroid adenomas in one of the Marshallese bows exposed in utere as of ine terest. Four children were exposed urate uy the higher radiation group, one at the end of unesec. ond trimester ad (woot dhe end of the first uri mmesters in the lower dose Ronygelap group, ane at (he cod of the second trimester, Ouly the boy in the higher dese group and cx posca in the second trimester has developed thyraid lesions. Several cases have been reported af children who had myxedema following a ates exposure during lreatsnent of the mother with barge doses of cadioiodine. PT LLowever,. this Marshallese buy ap. pears tobe the first reported case af thyroid adenos developing presumably drome waders expo sure to tacdiomdines. fates Uavroid dase calcuLidans are pot possible. since insufficient data are available on fetal thyroid uptake of racboiedines front the nother at Various stages of gestation! Figure 48 shows thy. roid function of the human fetus, The gland is not thought to begin to function and to accumulate iodine wndl about the Teh week of vestauon Phe At the tine of exposure ofthe Marshallese boy (about 22 to 24 weekso the Uhvroid should have been actively functioning. He received $73 rads of ganna radiation but the dase fron radioiadines is uncertain, In view of the high uptake of radicjodines per gram by the fetal thyroid at 22 weeks, the tivreid douse might be expected to be high. However, since i appeats from: our data that longer latent: periods are associated with lower doses of radiation tothe Ghyroid, His dikely drat the Uhivroid in this baw ex posed: audereeen cd a lower dose than thatia Marshallese children exposed ata voung aie. “Miso, this bay and the others exposed acatee have shown no dnpaurinens ta growth and development. Iois of uiterest (hac the mother of this bow has ed developed any thyreicd aboormalities and appears ta be curharoid. The two children exposed at the end al the first teamester probably had nonfincudoning primordial tiv. roid whines at dat Gane so that the wlhands gecewed only the gaia exposure and were therefore less lkeby tadeveiop thyroid abnornialities. None of the four childecn exposed acatero has show a tier. cephaly or mental retardation, which have been noted in some of the Children exposed gr ctere it Japan. V, Neoplasia Among the late cffeets af radiation, (he eabancement of the develapmeat of neoplasia his been well documented, Ea irradiated aninvals, malig. Hancies pot anky say be induced at an carer awe but appear in increased numbers, fa the Japanese atom booth sucvivers, loukeawa and thyroid neo: plasia have shawn the mast clear-cut asseciation with radiaven exposure, though more recently