2026 ETA Consensus Statement on the Interpretation and Management of Calcitonin Levels in Patients with Thyroid Nodules

Calcitonin (Ctn) is widely recognized as the most accurate test for the early detection of medullary thyroid carcinoma (MTC). Nevertheless, universal agreement on whether to routinely measure serum Ctn in all patients with thyroid nodules has not been achieved, mainly due to the perceived limited cost-effectiveness, the strict preanalytical workup needed for Ctn measurements, and the difficulties in interpreting borderline or mildly elevated Ctn concentrations in the presence of not fully interchangeable Ctn immunoassays. Although MTC is a rare malignancy, its prognosis is strongly dependent on the stage at diagnosis, that is strictly correlated to Ctn levels that reflect both the presence and burden of MTC. For these reasons the interpretation of preoperative Ctn concentrations, whenever performed, is critically important. This consensus aims to support clinicians who perform Ctn in the work up of thyroid nodules, either routinely or in accordance to the ETA guidelines, in decision-making when Ctn concentrations are above the upper reference limit, but not yet approaching or reaching the diagnostic levels, by identifying those who require surgery, those suitable for follow-up, and those who do not require further investigation.