Humoral markers for thyroid carcinoma.

We investigated the usefulness and limits of serum thyroglobulin, serum calcitonin, and serum tissue polypeptide antigen as humoral markers for thyroid carcinoma in 364 patients with papillary, follicular, medullary, and undifferentiated types of thyroid cancer. In agreement with other studies we found that serum thyroglobulin was a specific and sensitive marker for well-differentiated thyroid cancer after total thyroidectomy. Lymph node, lung, and bone metastases were associated with high serum thyroglobulin concentrations, both during and after thyroid-suppressive therapy with L-thyroxine. Serum thyroglobulin determination was superior to whole body scanning in predicting the presence of differentiated metastases, because patients with nonfunctioning metastases and negative whole body scan also had high levels of serum thyroglobulin. Serum calcitonin levels were increased in all patients with active medullary thyroid cancer, confirming the specificity of this marker in detecting tumors arising from parafollicular C-cells. Furthermore, in medullary thyroid cancer serum tissue polypeptide antigen levels were also increased in most patients. This last substance was found to be increased also in undifferentiated thyroid cancer. Of particular interest was the finding of increased serum tissue polypeptide antigen levels in 15 cases of differentiated thyroid cancer, whose metastases underwent a progressive process of "dedifferentiation."