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Research Article Free access | 10.1172/JCI106696
Department of Medicine, Harbor General Hospital, Torrance, California 90509
University of California Los Angeles School of Medicine, Los Angeles, California 90024
Find articles by Chopra, I. in: JCI | PubMed | Google Scholar
Department of Medicine, Harbor General Hospital, Torrance, California 90509
University of California Los Angeles School of Medicine, Los Angeles, California 90024
Find articles by Solomon, D. in: JCI | PubMed | Google Scholar
Department of Medicine, Harbor General Hospital, Torrance, California 90509
University of California Los Angeles School of Medicine, Los Angeles, California 90024
Find articles by Beall, G. in: JCI | PubMed | Google Scholar
Published October 1, 1971 - More info
A convenient, specific, precise, and reproducible radioimmunoassay system for measurement of triiodothyronine (T3) in human serum has been developed. The procedure compares the ability of standards and unknowns to compete with radioactive T3 for binding sites on a T3-binding antiserum produced in rabbits by immunization with human thyroglobulin. The assay is set up in the presence of 250 ng thyroxine (T4) in all tubes, to mobilize T3 from its binding with the thyronine-binding globulin (TBG), and athyreotic sheep serum in standards to correct for the TBG in the unknowns. The method regularly detected 0.4 ng T3, which would correspond to a T3 concentration of 100 ng/100 ml when 400 μl of serum is analyzed. The mean recovery of unlabeled T3 added to normal serum pools was 106%. Serial dilution of hyperthyroid sera containing high concentrations of T3 with athyreotic sheep serum yielded expected values.
The serum T3 concentration in 80% of 31 euthyroid normal subjects was less than 100 ng/100 ml (range < 100-170 ng/100 ml); it was greater than 170 ng/100 ml in 89% of 27 sera of hyperthyroid patients with untreated Graves' disease (range < 100-1300, mean 519 in 25 sera with detectable T3). The concentration of serum T3 fell, frequently to undetectable levels, during treatment of hyperthyroid patients with antithyroid drugs. The serum T3 concentration in four hypothyroid patients was less than 100 ng/100 ml.