[Characterization of thyroglobulin and thyroid peroxidase activity in patients with functioning thyroid benign...

The content and chemical and immunological properties of thyroglobulin (Tg) and the activity of thyroid peroxidase (TPO) were studied in nodular and extranodular (periphery) thyroid tissue from patients with functioning thyroid tumors (hot nodules). From the present observations, the tumor extracts contained fairly large amounts of Tg, similar to that in the periphery tissue, while the content of Tg was markedly decreased in non-functioning thyroid tumors (cold nodules). The iodine content of Tg was significantly higher in nodular tissue compared with periphery tissue. These observations were in contrast to the results seen in the cold nodules in which hormone synthesis was defective. On the nature of carbohydrate moiety as compared with normal tissue, oligosaccharides of Tg from the periphery tissues changed in a manner similar to that of tumor oligosaccharides. That is, high-mannose type oligosaccharides were markedly decreased whereas multiantennary and unidentified oligosaccharides were increased. These observations were similar to those of non-functioning tumors. The content of sialic acid decreased markedly both in the tumor and periphery tissues. Immunologically, Tg preparations of the tumor and periphery tissue did not show the same affinity to the antibodies, depending on the content of iodine. Therefore, it seems that the contribution of the iodine content and iodo-amino acid has little or no significance in the heterogeneous nature of Tg-immunogenecity. Benign tumors and the periphery tissue were subjected to assay for thyroid peroxidase activity by the method employing guaiacol as the second substrate. The specific activities of the tumors were generally higher than those of periphery tissues, both in functioning and non-functioning benign tumors. In non-functioning carcinoma, on the other hand, TPO activities were lower in tumor portions than in periphery portions. This indicates that non-functioning thyroid carcinomas have a different characteristic.