A Practical Radioimmunoassay of Thyroglobulin

We describe a reliable and convenient double-antibody radioimmunoassay for human thyroglobulin that can be performed within two days. Analytical recoveries were quantitative and immunological equivalence between several sources of human thyroglobulin was demonstrated. Cross reactivity with either thyroxine or triiodothyronine was insignificant. The between-day coefficient of variation in the 5-100 tg/liter range was 10%. The range observed for 68 normal individuals was 2-61 pg/liter. Additional Keyphrases: normal values thyroid dis-ease cancer diagnostic aids Increased concentrations of thyroglobulin are found in serum in a number of thyroid disorders, including thyroid tumors (1-6). The major interest in thyro-globulin determinations has centered on their use as aids in identifying and evaluating thyroid neoplasia. Although such measurements cannot help one to dis-tinguish benign from malignant disease, they reportedly are useful for detecting thyroid neoplasia among indi-viduals with a history of head and neck irradiation during childhood (5). Perhaps the most valuable ap-plication of thyroglobulin assays has been to the post-treatment follow-up of patients with differentiated thyroid carcinoma. After successful therapy, concen-trations of thyroglobulin decreased to and remained normal; however, in patients with metastases, they ei-ther increased further or increased again after declining (4,6). In response to the growing interest in thyroglobulin measurements, we have developed and validated a RIA that is designed for the clinical laboratory. This assay is performed in conjunction with a sensitive test for detecting interfering autoantibodies, described in an accompanying paper (7)