Serum Level of Protein Bound Radioactive Iodine (I 131 ) in the Diagnosis of Hyperthyroidism. *

Abstract

Summary

1. The serum protein bound radioactive iodine (I¹³¹) level was determined 24 hours after the oral administration of 150 microcuries I¹³¹. Twenty subjects were studied; 10 were thyrotoxic and 10 euthyroid. The protein bound I¹³¹ was determined by a modification of the method described by Chaikoff et al. ⁸

2. The serum protein bound I¹¹³ in thyrotoxic patients was 38 to 146 × 10⁻⁵ microcuries/cc averaging 68. In euthyroid subjects, the serum level ranged from 3 to 28 × 10⁻⁵ microcuries/cc, averaging 13.

3. It would appear that this test may be of diagnostic value as a measure of thyroid function.