SERUM THYROGLOBULIN IN THE DIAGNOSIS AND MANAGEMENT OF THYROID CARCINOMA

Abstract

Serum thyroglobulin (Tg) was measured by radioimmunoassay in 62 control subjects, 163 euthyroid patients with nodular goiter and 81 patients with previously treated differentiated thyroid carcinoma. Tg was elevated in 65% of nodular goiters and failed to fall with thyroxine treatment in 10/15 patiens treated. A diagnosis of differentiated carcinoma was confirmed in 14/64 of these patiens and Tg was elevated in 12. Of 65 treated thyroid carcinoma patients without evidence of residual tumor, serum Tg was undetectable in 39, normal in 24 and elevated in 2. There was evidence of residual tissue in the thyroid in 17 patients with detectable Tg. Of the 16 patients with residual tumor or metastases Tg was elevated in 15. There was a positive correlation between goiter size and Tg levels in multinodular goiter, and thyroid carcinomas of large bulk were associated with higher Tg levels. Serum Tg was normal in medullary carcinoma and in 2 patients with thyroid metastases from extra-thyroidal malignancies. High Tg levels in patients with residual metastases from thyroid carcinoma following thyroid ablation indicates production by tumor tissue. Measurement of serum Tg of limited value in the differential diagnosis of nodular thyroid disease. It is particularly useful following surgery and 131I therapy for differentiated thyroid carcinoma. In these patients it gives confirmation of thyroid ablation and may provide evidence of residual tumor tissue when other tests are negative.