A cut-off value of basal serum calcitonin for detecting macroscopic medullary thyroid carcinoma

SummaryObjective Serum calcitonin (CT) level is used to detect medullary thyroid carcinoma (MTC), but the cut-off level is unclear. We aimed at identifying the optimal cut-off value of basal serum CT levels for detecting MTC. Design and patients We retrospectively enrolled patients with hypercalcitoninemia (≥2·9 pmol/l) who had undergone thyroid ultrasonography (US) and subsequent work-up between 2001 and 2013 at Asan Medical Center. We divided patients into four groups: proven MTC (group 1, n = 93), pathologically proven non-MTC after surgery (group 2, n = 57), benign single nodule by cytology (group 3, n = 68) and patients without nodules on US (group 4, n = 24). Measurement Basal serum CT levels were evaluated. Results The median CT level of group 1 (119·5 pmol/l) was significantly higher than those of other groups (4·0, 3·8 and 3·8 pmol/l, P