Sate ~ ce c yet ax BR AFF / 1230 NATIONAL INSTITUTES OF HEALTH CLINICA U : TABLE 5, Date . et ay a STA eon ng oO - eo ; Annals of Internal Medicine Serum Iodide Measurements in the Marshall Islands Group No. . Average Samples — ° . J - Range Dts Percent Over 8 ug/ 100 m] Protein-bound-iodine, ug/l00 mi Marshallese Marshallese Medical team Marshallese—exposed Marshallese—unexposed 12, 14 10 31 19 Butanol extractable iodine, zg/ JOO mi 1959 Marshallese 12 level and individual values going up well into the hyperthyroid range. In 1965 a comparison was carried out be- tween exposed and nonexposed individ- uals; there was no difference between them. One evaluation of the butanol extractable serum iodine (BEI) done as far back as 1959 indicated that the BEI—which would be the hormonal itodine—was in the nor- mal range for North America, suggesting that the elevated PBI was not thyroxine- like. Figure 14 shows the distribution of the PBI in the population. The valley at one point was thought to be an artifact due to the small number of individuals sampled, and it was concluded that the PBI levels formed a normal distribution. There was no bimodal distribution or any familial w# 8 CASES _ 6.2 8.6 4.9 7.6 «0 "49 / * 4.1-9.2 46-12.0 2.5-6.9 . 41-11.9 —3.9-10.7 16 64 0 42 28 : .. 2.7-8.7 prevalence that would indicate a genetic abnormality or any evidence of two genetic populations in the Islands with respect to PBI levels in blood. Table 6 shows some later studies in which chromatography on Dowex-1 columns was performed in order to identify the nonhormonal iodine in serum. This procedure (15) separates iodoprotein from iodoamino acids not in peptide linkage. In North Americans (these were normal controls drawn at the NIH) the iodoprotein averaged 0.8 »g/100 ml, whereas in the Marshallese the value was considerably higher with a mean of 2.2 wg/100 mI. The thyroxine iodine average was slightly higher in the Marshallese but probably not significantly. . Recently, with the development of thyroid abnormalities in the exposed Marshallese, it was possible to examine serum iodoprotein levels in patients with thyroid hypofunction. The results, presented in Table 7, suggest that the todoprotein was largely from an extrathyroidal source since the level was still elevated in patients with 4 6 8 PBI to 12 pg /l90 mi Ficure 14. Distribution of serum protein-bound iodine in Marshallese individuals. Reproduced with permission from Rall and Conard: Amer. J. Med. 40: 882, 1966 (12). atrophic thyroid glands due to radiation (Cases 3 and 5); in thyroidectomized patients, one of whom (Case 69) had little, if any, uptake of #*7J into the thyroid (as we will discuss later); and in subjects who had been on suppressive therapy with levothyroxine, Dr. Conard mentioned that the iodine analyses of urine, which were carried out ee 1959 1962 1964 1965 1965