[Katacalcin--a new tumor marker in C-cell cancer of the thyroid gland].

Katacalcin (KC) is situated on the C-terminal side of the procalcitonin molecule and is cleaved like calcitonin (CT) from this precursor peptide. Serum levels of KC were measured in 22 patients with C-cell carcinoma with a specific and sensitive radioimmunoassay (normal range, less than 0.1-0.15 ng/ml). Basal serum KC values in C-cell carcinoma patients were 0.32-290 ng/ml. There was a good correlation between KC and CT (r = 0.98, P less than 0.001). Serum KC, as well as CT, markedly increased after pentagastrin and calcium infusion. KC and CT were secreted in nearly equimolar amounts. During selective venous catheterization, KC and CT levels were increased in serum samples from veins draining tumor masses, which could be confirmed operatively. During the follow up, KC and CT measurements correlated well to the stage of disease. KC could be immunohistologically localized in C-cell carcinoma tissue. As a tumor marker, katacalcin is likely to be as useful as calcitonin in C-cell carcinoma.