ae! , . stature among the boys exposed at less than 10 years of age. The differences arestatistically significant only between ages g and 16, apparently because thyroid medication was administered to the exposed people on Rongelap after 1963. Figure 1 also showsthat statural retardation occurred in both sub_sups (age 0 to 5 and 5 to 10 at exposure) but was more ..arked in the younger subgroup. Statural growth in the few boys exposed at greater than 10 years of age showed nodifferences from that in unexposed boys. Amongthegirls, the statural growth curve (Figure 1) for those exposed to fallout at age 0 to 10 wassignificantly retarded at chronologic ages of 6 to 7 years, compared with that for the unexposedgirls. Figure 1 also showsthat the statural retardation occurred in girls exposed at less than 5 years of age but not in those exposed at age 5 to 10, and disappeared “y about age 9. The curvesfor girls exposedat age 10 to 18 are uite similar to those for unexposedgirls. These findings suggest that retardation in stature among the exposed girls occurred earlier and was less prominent and of shorter duration than that among the exposed boys. Osseous Maturation Osseous maturation among exposed boys wassignificantly retarded compared with that in unexposed age peers (Figure 2), This retardation was particularly prominent when the ovs were 14, 15, and 16 years of age, and as can be seen in Figure 2, retardation occurred in both age groups (those age <5 and age 5 to 10 in 1954). Figure 2 also shows a similar comparison amonggirls. For the entire group exposed at less than 10 years of age, skeletal maturation lagged significantly behind that in the unexposed girls until about age 10, and thereafter the gap progressively narrowed. Figure 2 suggests that this retardation in osseous maturation among exposedgirls occurred primarily among ‘hose exposed at less than 5 years of age and to a very limited ‘legree in those exposedat age 5 to 10. Statistical analyses of the data on adult(final) stature of the Rongelap inhabitants who were in the pediatric age group on March 1, 1954, gave the following results: e In the unexposed group. for both boysandgirls, there was no significant difference in mean adult stature between those born after 1944 (<10 years old on March 1, 1954) and those born before 1945 (>10 years old on March1, 1954). e in the exposed group, for both boys and girls, there was no significant difference in mean adult stature between those born after 1944 and those born before 1945. ® For both boys and girls, there was no significant difference in mean adult stature between those who were exposed to fallout radiation on Rongelap and Ailingnae and those who werenot. Since osseous maturation is dependent on normalthyroid function, it is reasonable to assumethat its retardation in exposed children was due to radiation damage to the thyroid glands. The marked retardation of skeletal maturation followed by dramatic improvementafter the administration of thyroid hormone has been documented in the children who were Clinically hypothyroid.’ The catch-up phenomenon in osseous maturation can reasonably be attributed to the administration of thyroid hormone to the exposed populations, many of whom weresubclinically hypothyroid. Acknowledgments The submitted manuscript has been written under contract DEAC02-76CH90016 with the US Department of Energy. Accordingly, the US Governmentretains a nonexclusive, royalty-free license to publish or reproduce the published form of this contribution, or allow others to do so, for US Government purposes. The authors wish to thank the many physicians and technicians, from both the United States and the Trust Territory of the Pacific Islands, for their assistance, and particularly the Marshallese people, for their cooperation in the performance of the examinations. Comments Growth studies on young people exposed to radiation from atomic bombs in Hiroshima and Nagasaki showed that their adult heights were significantly lower than those of the controls.** Similar analyses were carried out on statural data from inhabitants of Rongelap and Ailingnae Atolls who were exposed as children to fallout radiation. The presumptive adult inal} stature is either the plateau value when several measurements remained the same, or the latest measurement (made when the subject was 20 years of age) if the latest prior measurement had continued to show increase. It is generally assumed that adult height is attained when the skeletal age is 17 to 18 years in girls and 18 to 19 in boys,'*75"* but actual measurements on the Marshallese popu- lation showed that many subjects continued to increase in Stature with advancing chronologic age, even after age 30, although the late increments were almost always very small. \fter the Marshallese reached 16 years of age, absences from the island at the time of survey became more frequent; therefore, the time when adult stature was actually attained is unCertain for many individuals. References 1. Conard RA, Paglia DE, Larsen PR,et al: Review of medicalfindings in a Marshallese population twenty-six years after accidental exposureto radioactive fallout, Brookhaven National Laboratory report BNL 51261. Upton, NY, Brookhaven National Laboratory, January 1980. 2. Conard RA, Knudson K, Sutow WW,et al: A twenty-year review of medicalfindings in a Marshallese population accidentally exposed to radioactive fallout, Brookhaven National Laboratory report BNL 50424. Upton, NY, Brookhaven National Laboratory, 1975. 3. Conard RA, Sutow WW, DobynsBM,et al: Medical survey of the people of Rongelap and Utirik Islands thirteen, fourteen, and fifteen years after exposure to fallout radiation (March 1967, March 1968, and March 1969), Brookhaven National Laboratory report BNL 50220 (T-562). Upton, NY, Brookhaven National Laboratory, June 1970. 4. Conard RA: A case of acute myelogenous leukemia following fallout radiation exposure. JAMA 232:1356-1357, 1975. 5. Larsen PR, Conard RA, KnudsonK,et al: Thyroid hypofunction after exposure to fallout from a hydrogen bomb explosion. JAMA 247:1571—-1575, 1982. 6. Sutow WW,Conard RA, Griffith KM: Growth status of children THE CANCER BULLETIN, VOL 34, NO 3, 1982 95