+2 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 thyroid gland and signs of myxedema with puffy faces, dry skin, sluggish reflexes, and bony dysgenesis of the humerus and femur (see Figure 28). These two boys (Nos. 3 and 5) were considerably shorter than their brothers (Nos. 83 and 84) who were younger and had been exposedin utero. In 1965, a satisfactory method for serum thyroxine analysis by ion exchange column becameavailable. Stud- the thyroid gland. Developmentof thyroid abnormalities in other subjects continued during subsequentyears.'8-23 At present (197+) 29 of 86 exposed people of Rongelap are affected, including the two stunted boys who developed thvroid atrophy without nodularity. One of + children exposed in utero developed thyroid nodules in 197+. Figure 29 showsthat, considering the population remainingatrisk (persons living in 1964, at the time of appearanceof the thyroid abnormalities), the trendis for continued developmentoflesions with recent increases among the lower-exposure Ailingnae group. Table 24lists the thyroid status ies by this method showed that someof the children did indeed havelow serum thyroxinelevels. of all exposed Rongelap people and of people with tein levels, leading to a false interpretation ofpro- were not tender, and varied in size from several Control studies on normal Marshallese revealed that manyof them had unusually high iodopro- tein-boundiodine (PBI) determinations. It became apparent only then that low thyroxine (T4)levels positive findings in certain other populations. The thyroid nodules were usually multiple, millimeters to several centimeters in diameter. In some of the children nodular glands were associ- ated with low thyroxine levels and slight growth in someof the children had probably been masked by high levels of iodoprotein.!8-23 Several children with slight growth retardation had lowered Ty levels. The hypothyroidism appeared to be from primary thyroid damage and not secondary to retardation. The two stunted boys (Nos. 3 and 5) showed markedly reduced thyroxine levels. None of the aduits with nodularity had low thyroxine in several growth-retarded children were normal,and their serum thyroid-stimulating hormone be the result of radiation injury to the thyroid in the children (see Section E, below). pituitary damage,since tests for growth 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 levels prior to surgical exploration. The growth retardation with reduced thyroxine levels appears to 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 incidenceoflesions (89.5%) has been noted amongthose in the heavily exposed group who were <10 years old at the time of the acci- dent. The absence of lesions among those ofcorresponding ages in the less exposed Utirik group and the unexposed groups is notable, but 2 of 6 ex- posed children in the Ailingnae group have re- Percent thyroid 30 cently developed lesions. The incidence of thyroid lesions among the exposed Rongelap adults is considerably lower than that amongthe children buc higher than among the Utirik or unexposed groups. The Utirik group does not appear to have had a higher incidence of thyroid lesions than the unexposed groups, but one Utirik individual developed cancer of the thyroid. a +0 e3 = 30 a 3 20 2 & 10 10 Ib i i ies 61206 «130 «14: = 6150 (160 OL? 1B 19) 0 Years after exposure Figure 29. Cumulative percentages of persons with thy- roid lesions in exposed Rongelap, Ailingnae, and Utirik groups and in unexposed Rongelap controi groupsince 1964, based on numbers of persons in the groups in 1964, the time when radiation-inducedlesions were first noted. C. SURGICAL EXPLORATION In view of the possibly malignant nature of the thyroid nodules in the exposed population,surgical exploration of the affected thyrdids, with removal of nodules, was considered necessary. Thy-