[Radioimmunologic analysis in the differential diagnosis of cancer of the thyroid gland].

Investigations using a radioimmunoassay in 92 patients with nodular goiter, thyroid adenoma and cancer have shown that changes in the levels of T4, T3 and TSH cannot be used in differential diagnosis of tumors. A high level of thyroglobulin (TG) in 70-75% of patients in the absence of antibodies to it and the presence of a "cold node" on a scan is suggestive of differentiated types of thyroid cancer. In these cases TG can serve as a tumor marker. A moderate level of Tg in 25-30% of cases against a background of a high level of antibodies to it does not permit its use as a tumor marker in such patients even in the postoperative period. High levels of TG and TSH despite the use of thyroid drugs in patients, operated on for differentiated types of thyroid cancer, may be suggestive of a possible manifestation of a recurrence or metastatic spreading.