42 8 years post exposure it was noted that two boys were particularly stunted in growth (Figure 27).10-16 They had been exposed at one year of age and gradually developed atrophy of the thvroid gland and signs of myxedema with puffy faces, dryskin, sluggish reflexes, and bonydysgenesis of the humerus andfemur(see Figure 28). These two bovs (Nos. 3 and 5) were considerably shorter than their brothers (Nos. 83 and 84) who were vounger and had been exposed zn utero. In 1963, a satisfactory method for serum thyroxine analysis by ion exchange column became available. Studies by this method showed that some ofthe children did indeed have low serum thyroxinelevels. Control studies on normal Marshallese revealed that many of them had unusually high iodoprotein levels, leading to a false interpretation of pro- tein-boundiodine (PBI) determinations. It became apparentonly then that low thyroxine (T4) levels in some of the children had probably been masked bv high levels of todoprotein.!8-23 Several children with slight growth retardation had lowered T4 levels. The hypothyroidism appeared tobe from primary thyroid damage and not secondary to pituitary damage, since tests for growth hormone in several growth-retarded children were normal, and their serum thyroid-stimulating hormone (TSH) levels were elevated. B. DEVELOPMENT OF THYROID NODULES In 1963, 9 years after exposure, a 12-year-old girl was found to have an asymptomatic nodule of t - Percent thyroid > 30; ~~ 2 ol a 2 5 2 & 2 | e Rongelap ao 2 Utirik Control 2 | 1 18 19 <Ailingnae yt “a el] = 10 tt 2 13 14 15 16 17 the thyroid gland. Development of thyroid abnor- malities in other subjects continued during subsequent years.!8-?3 At present (1974) 29 of 86 ex- posed people of Rongelapare affected. including the two stunted bovs who developed thyroid atrophy without nodularity. Oneof 4 children exposed in utero developed thyroid nodules in 1974. Figure 29 shows that, considering the population remainingat risk (personsliving in 1964, at the time of appearanceof the thyroid abnormalities), the trend ts for continued developmentof lesions with recent increases among the lower-exposure Ailingnae group. Table 24 lists the thyroid status of all exposed Rongelap people and of people with positive findings in certain other populations. The thyroid nodules were usually multiple. were not tender, and varied in size from several millimeters to several centimeters in diameter. In some of the children nodular glands were associated with low thyroxine levels and slight growth retardation. The two stunted boys (Nos. 3 and 3) showed markedly reduced thyroxine levels. None of the adults with nodularity had low thyroxine levels prior to surgical exploration. The growthretardation with reduced thyroxine levels appears to be the result of radiation injury to the thyroid in the children (see Section E, below). Table 25 lists the incidence of benign and malignant lesions and the estimated dose of radiation to the thyroid glands in the various populations The highest incidence of lesio- (89.5%) has been noted amongthose in the heavily exposed group who were < 10 years old at the time of the accident. The absence of lesions among thoseof correspondingagesin the less exposed Utirik group and the unexposed groups is notable, but 2 of 6 exposed children in the Ailingnae group have recently developed lesions. The incidence of thyroid lesions amongthe exposed Rongelapadultsis considerably lower than that amongthe children but higher than among the Utirik or unexposed groups. The Utirik group does not appear to have had a higherincidenceof thyroid lesions than the unexposed groups, but one Utirik individual developed cancer of the thyroid. 20 Years after exposure Figure 29. Cumulative percentages of persons with thy- roid lesions in exposed Rongelap, Ailingnae, and Utirik groups and in unexposed Rongelap control group since 1964, based on numbers of persons in the groups in 1964, the time whenradiation-inducedlesions were first noted. C. SURGICAL EXPLORATION In view of the possibly malignant nature of the thyroid nodules in the exposed population, surgtcal exploration of the affected thyroids. with removal of nodules, was considered necessary. Thy-