Serum Level of Protein Bound Radioactive Iodine (I131) in the Diagnosis of Hyperthyroidism.

Abstract

The serum protein-bound radioactive iodine (I131) level was detd. 24 hrs. after the oral admn. of 150 microcuries of I131. 20 subjects were studied; 10 were thyrotoxic and 10 euthyroid. The protein-bound I131 was detd. by a modification of the method descr. by Chaikoff. (Endocrinology 40: 47. 1947). The serum protein-bound I131 in thyrotoxic patients was 38-146 x 10-5 microcuries/cc. (avg. 68). In euthyroid subjects the serum level ranged from 3-28 x 10-5 microcuries/cc. (avg. 13). It would appear that this test may be of diagnostic value as a measure of thyroid function.