EFFECT OF THYROTROPIN ON THE SERUM PROTEIN-BOUND IODINE LEVEL IN VARIOUS THYROID STATES (TSH-PBI TEST)*

Abstract

Single intramuscular injections of thyroid-stimulating hormone (TSH) were given to 22 normal subjects and to 67 patients with abnormal thyroid or anterior pituitary glands. Resulting changes in serum protein-bound iodine (PBI) concentration were measured. Among the normal subjects PBI concentrations had risen to maximal heights by the fifteenth hour after injection when the dose was 101. U. andby about the twentieth hour when the dose was 20I. U. In both cases maximal elevations of of PBI concentration were maintained beyond the twenty-fourth hour. Twenty-four hours after injection of 5,10 or 20I. U., the mean rises in PBI concentra-tion for the normal subjects were 1.3 [mu]g[plus or minus]0.6(S.D.),2.2[mu]g[plus or minus]0.6, and2.8 [mu]g[plus or minus] 1.0 per 100 ml., respectively. Among the patients, determination of rises in PBI concentration twenty-four hours after injection of 10I. U. revealed that, with exceptions, responses were abnormally low in patients with diffuse thyroid disease whereas they were normal in patients with focal thyroid disease or pituitary failure. In some patients with nontoxic nodular goiter, the responses were abnormally high. Tests of this kind may be useful in distinguishing between a) Hashimoto''s disease and other non-toxic nodular goiters, b) Graves'' disease and toxic nodular goiter, and c) primary and secondary myxedema.