Further Observations on the Occurrence of the Thyrotropin Inhibitor in Urine

Abstract

The investigation of factors affecting thyrotropin inhibitor (TSH-I) in urine of patients and euthyroid individuals has been continued. A modified procedure for chick thyroidal radioiodine release for the bio-assay of TSH and a benzoic acid concentration procedure of TSH-I of urine is described. TSH-I preparations from 5-day urine collections revealed minimal presence of TSH-I only in 3 of 10 untreated hypothyroid patients, while the administration of Na-L- or Na-D-thyroxine to euthyroid subjects, hypothyroid and hyperthyroid patients, or radioiodine treatment in hyperthyroid patients invariably resulted in increasing titers of TSH-I. The rise in TSH-I could be correlated with elevation of serum proteinbound iodine levels and reduction of serum cholesterol levels, usually occurring during the first 3 weeks following increase of the medication dose. The increased TSH-I titer reached a peak, followed by a period of adjustment and, in most cases, by a decrease of TSH-I thereafter.