Serum Protein-Bound Iodine—Rall and Conard 886 This agrees fairly well with the figure of 76 ug. per day calculated independently from urine and radioiodine studies and is compatible with the clinical picture of a euthyroid status despite an elevated PBI level and an increased thyroid iodine secretion rate. The depressed thyroidal iodine uptake rate and renal excretion rate are puzzling and no explanation for them is available at this time. in serum proteih-hourr iodine (PBI) seems to be general throughout the population since’ the distribution curve of serum PBI is simple. Column chromatography of the serum iodine in twenty-five normal subjects in the United States shows average values of iodoprotein of 0.8 wg. per cent and of thyroxine plus triiodothyronine of 3.8 we. per cent whereas in the Marshallese the average iodoprotein level was 2.2 weg. per cent and thyroxine plus triiodothyronine 4.5 wg. per cent. The high iodoprotein levels appeared to account for the in- crease in serum PBI in the Marshallese. The thyroidal iodide clearance and the renal iodide clearance in the Marshallese were both depressed to approximately one half of normal. The amountof iodine secreted by the thyroid in the Marshallese was estimated to be 76 ug. per day. 3. Gatton, V. A. and Pittr-Rivers, R. A quantitative method for the separation of thyroid hormones and related compounds from serum and tissues with an anion-exchange resin. Biochem. J., 72: 310, 1959. . Hetiman, E. S., Tscxxupy, D. P., Ropains, J. and Endocrinol., 23: 1185, 1963. . Rosas, J. Reverse flow zone electrophoresis. A method for determining thyroxine-binding capacity of serum protein. Arch. Biochem., 63: 461, 1956. . Berman, M., Suan, E. and Weiss, M. F. A digital computer program for the analysis of kinetic data. Biophys. J., 2: 275, 1962. . Kypp, D. M., Man, E. B. and Perers, J. P. Con- centration of precipitable iodine in the serum. J. Clin. Invest., 29: 1033, 1950, . Man, E. B., Kypp, D. M. and Perers, J. P. Butanol-extractable iodine of serum. J. Clin. Invest., 30: 531, 1951. . Rau, J. E. The role of radioactive iodine in the diagnosis of thyroid disease. Am. J. Med., 20: 719, 1956. 10. Stansury, J. B., BRowNELL, G, L., Ricas, D. 5., Peretti, H., Iroiz, J. and Det CastTiL_o, E. B. Endemic Goiter—The Adaptation of Man to Iodine Deficiency. Cambridge, 1954. Harvard University Press. 11. Incpar, S. H. and Freincer, N. Simultaneousestimation of rates of thyroxine degradation and thyroid hormone synthesis. J. Clin. Invest., 34: 808, 1955. 12. Rices, D. S. Quantitative aspects of iodine metabolism in man. Pharmacol, Rev., 4: 284, 1952. 13. BEreERWALTES, W. H. and Rossins, J. Familial increase in the thyroxinebinding sites in serum alpha globulin. J. Clin. Inzest., 38: 1683, 1959. REFERENCES 1. Conarp, R. A., Ropertson, J. S., Mever, L. M., W., Worins, mination of protein-bound iodine in serum. Clin. chim, acta, 5: 301, 1960. iodine in acute intermittent porphyria. J. Clin. From 20 to 40 per cent of the people living on an atoll in the Marshall Islands have elevated serum protein-bound iodine levels without evidence of hyperthyroidism. The increase W. 2. Foss, O. P., Hanxes, L. V. and Van Sryxe, D. D. A study of thealkaline ashing method for deter- Ratt,J. E. Elevation of the serum protein-bound SUMMARY Sutrow, (T-135), Washington, D. C., May, 1959. U.S. Department of Commerce. W., Lowrey, A., Urscnuer, H. C., Jr., Barron, J. M., GoLtpman, M., Hecuter, H., Ercuer, M., Carver, R. K. and Porter, D. W. Medical Survey of Rongelap People, March 1958, Fours Years After Exposure to Fallout. Brookhaven National Laboratory 534 14, Rossing, J., Razzi, J. E. and Rawson, R. W. A new serum iodine component in patients with functional carcinoma of the thyroid. J. Clin. Endo- ertnol., 15: 1315, 1955. 15. Tata, J. R., Ratt, J. E. and Rawson, R. W. Studies on an iodinated protein in the serum of subjects with cancer of the thyroid. J. Clin. Endorcinol., 16: 1554, 1956. Reprinted from the June issue of The American Journal of Medicine volume 40, number 6, pages 883-886, copyright 1966 and printed in the U.S.A. Published by The Reuben H. Donnelley Corporation, 466 Lexington Ave., New York 10017