FALLOUT EFFECTS—MARSHALL ISLANDERS 61 than 5 years of age. Retrospective analyses of the frozen serum samples revealed that many of the children, prior to thyroid surgery, had elevated TSH levels and in somecases reduced T, levels, though except for the two myxedematous boys, the hypofunction was not severe enough to be clinically evident. In 1965 T, (synthroid) treatment was instituted in exposed Rongelap and Ailingnae populations with the objectives of retarding thyroid nodule formation and enhancing growth and development in growth-retarded children. It was given to surgical cases only in the Utirik and control populations. Results of this treatment will be discussed below. In view of the early hypofunction of the thyroid noted in the children, the groupstested for hypofunction have included, in addition to the exposed Rongelap-Ailingnae groups, the exposed Utirik people and many unexposed people. On the basis of control studies in the unexposed Marshallese, an increase in TSH level to 26 »U/mi on at least two occasions was considered positive evidence of hypofunction and levels between 3 and 6 ~»U/mi were considered suggestive evidence. In some of the exposed children, the evaluation was based on only one available presurgical sample (13,37). These are very sensitive criteria and represent subclinical or “biochemical” hypofunction. In addition to TSH analyses, results of stimulation tests with TSH and TRH were used in many cases to confirm the findings. Table 2 summarizes these findings. The most marked TSH elevations were noted in the Rongelap people exposed at less than 10 years of age, who had received the highest thyroid doses. Only two of these had clinical hypothyroidism, and most of the others subsequently TABLE 2. Thyroid hypotunction (1981) Hypofunction Group age 1954 Rongelap 1 yr 2-10 210 Ailingnae <10 210 Utirik < 10 = 10 Controls <10 210 Est. dose (rads) No. Positive OO No. % Positive + Suggestive No. % 2 1500(?) 800-1500 335-800 ; 275-450 135-190 6 16 45 5 4 4 83 25 9 5 8 6 83 50 13 7 12 0 1 0 8 0 2 0 17 60-95 30-60 64 100 0 1 0 1 4 4 6 4 229 371 1 1 0.4 0.3 2 2 0.8 0.5 2 The levels in the exposed groups have not been corrected for control levels, since the correction would be small. Includes presurgical data.