+2 8 years post exposure it was noted that two boys were particularly stunted in growth (Figure 97),10.16 They had been exposed at one year of age and gradually developed atrophyof 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 bovs (Nos. 3 and 5) were considerably shorter than their brothers (Nos. 83 and 8+) who were vounger and had been exposed in uler>. In 1963, a satisfactory methodfor serum thyroxine analysis by ion exchange column becameavailable. Studies by this method showed that some ofthe children did indeed have low serum thyroxinelevels. Control studies on normal Marshallese revealed that manyof them had unusually high iodoprotein levels, leading to a false interpretation of protein-bound iodine (PBI)determinations. It became apparent onlythen that low thyroxine (T4)levels in some of the children had probably been masked by high levels of iodoprotein.!8-73 Several children with slight growth retardation had lowered T, 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 | Percent dhyroaid lesions (cumulative) - 30 #0 10 e@ . : Ailingnae 4 Control if : 7 i Rongelap 5 oO ‘ 7 Utink on woh. 12 be #13 T ele 14 ook #150 a ee the thyroid gland. Development of thyroid abnormalities in other subjects continued during subsequent years.!3-?3 Ar present (1974) 29 of 86 exposed people of Rongelap are affected, including the two stunted boys who developed thyroid atrophy without nodularity. One of 4 children exposed m utero developed thyroid nodules in 1974. Fig..e 29 showsthat, considering the population remaining at risk (persons living in 1964, at the ume of appearance of the thyroid abnormalities), the trend is for continued developmentoflesions 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 wereassociated with low thyroxine levels and slight growth retardation. The two stunted boys (Nos. 3 and 5) showed markedly reduced thyroxine levels. None of the adults with nodularity had low thyroxine levels prior to surgical exploration. The growth retardation 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 oflesions (89.5%) has been noted amongthose in the heavily exposed group who were <10 years old at the time of the accident. The absence oflesions among those ofcorresponding ages in 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 among the exposed Rongelap adults is 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 higherincidence of thyroid lesions than the unexposed groups, but one Utirik individual developed cancerof the thyroid. «160~6«17)«18 Years after exposure Figure 29. Cumulative percentages of persons with thyroid 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 when radiation-induced lesions were first noted. C. SURGICAL EXPLORATION In view of the possibly malignantnature of the thyroid nodules in the exposed population, surgical exploration of the affected thyroids, with removalof nodules, was considered necessary. Thy-