Abnormal Gamma Globulin Binding of Thyroid Hormones

Abstract

Thyroid hormone levels were studied in a thyrotoxic patient, who was treated with propylthiouracil. He had heavily increased triiodothyronine [T3] concentrations, measured by radioimmunoassay [RIA], in spite of only mild clinical symptoms of thyrotoxicosis. A moderately increased serum T3 concentration was observed in another patient, who was euthyroid and who had recently recovered from subacute thyroiditis. By gel electrophoresis and precipitation tests with human anti-Ig[immunoglobulin]G and anti-IgA, a binding to the gamma globulins of both T3 and thyroxine was detected in patient 1, and of T3 in patient 2. Such abnormal binding may result in serious errors in the determination of thyroid hormone concentration by RIA.