Postoperative pentagastrin-stimulated serum calcitonin concentrations in patients with medullary thyroid carcinoma: reoperations in patients with concentrations bordering the detection limit.

The case reports on two patients with medullary thyroid carcinoma show that even postoperatively stimulated serum calcitonin (CT) concentrations near the detection limit (using a polyclonal antibody against synthetic CT) can demonstrate persistent disease. Stimulated CT concentrations can be lowered to nondetectable levels by a second and third operation if a meticulous technique is used for dissection of the lymph compartments. The patient can then be assumed to be cured. Diagnostic accuracy at very low CT concentrations can be improved by selective venous catheterization with blood sampling for CT after stimulation.