Control of treatment of differentiated thyroid carcinoma by measurement of thyroglobulin in serum

The presence of thyroglobulin in serum of patients with differentiated thyroid carcinoma was studied by a specific radioimmunoassay. We examined 73 patients with thyroid carcinoma, 16 of which had pulmonary or sceletal metastases, 11 local metastases, and the other no metastases. Patients with generalised metastases had very high serum thyroglobulin concentrations while those with local metastases had slighly elevated or normal concentrations. Those with remaining thyroid tissue had mainly normal thyroglobulin levels and patients with neither metastases nor remaining thyroid tissue had undetectable serum thyroglobulin. In 7 patients with metastases we were able to observe the development of serum thyroglobulin after 131-iodine treatment. In all cases the serum thyroglobulin concentration paralled the development of the clinical status. Elevated serum thyroglobulin was also found in benign thyroid diseases such as hyperthyroidism and endemic goiter. Measurement of thyroglobulin in serum is therefore of little value in differentiating between benign and malignant thyroid diseases, but a good method for the follow-up control of patients with differentiated thyroid carcinomata. Because normal thyroglobulin levels do not exclude local metastases, additional examinations are necessary if normal thyroglobulin levels are found. When thyroglobulin is undetectable, metastases can be excluded and the measurement of thyroglobulin in serum can replace all other methods in the follow-up control. (orig.)