The Concentration and Significance of the Butanol-Extractable I131 of Serum in Patients with Diverse States of Thyroidal Function

Abstract

Iodine-containing material extractable from serum with butanol and not re-extractable with alkali (butanol-extractable iodine or BEI) was shown to consist largely of thyroxin. Measurements were made of the concn. of radioactive BEI in the serum of 109 patients with various states of thyroidal function following tracer doses of I131. Results were correlated with the 24-hr. thyroidal uptake of radioiodine and with the subsequent change in thyroidal radioiodine content during the 24-72 hr. period. Analysis of results reveals that concn. of BEI131 in the serum is dependent on initial thyroidal uptake of I131, rate of synthesis of thyroidal hormone, and amt. of hormone stored within the gland. The 72-hour concn. of the BEI131 correlates well with the clinical state except in nonthyrotoxic patients in whom the quantity of hormone stored within the gland is markedly decreased.