Increased calcitonin level in thyroid nodules without medullary carcinoma

Basal calcitonin measurement is routinely performed in patients with a thyroid nodule to detect medullary carcinoma. However, increased calcitonin does not always correlate with medullary carcinoma. The aim of this study was to analyse increased calcitonin levels in patients without medullary carcinoma and to find out whether absence of this carcinoma can be predicted with certainty.

From 1992 to 2003, 5018 patients with thyroid nodules underwent thyroid surgery. A retrospective analysis of preoperative increased calcitonin levels in 67 of these patients was performed.

Pathology revealed medullary carcinoma in 16 patients (group I), micromedullary carcinoma in 13 (group II) and no medullary carcinoma in 38 (group III). In group III, 30 patients had C-cell hyperplasia. The mean basal calcitonin level was 6250 pg/ml in group I (39-62 500), 109.6 pg/ml in group II (10-728) and 25.5 pg/ml in group III (10.5-145). The mean pentagastrin-stimulated calcitonin level was 1074.1 pg/ml in group II (26-5700) and 67.6 pg/ml in group III (10-205).

There is an overlap of thyroid C-cell pathology for medullary carcinoma, micromedullary carcinoma and C-cell hyperplasia that occurs when basal calcitonin is between 10 and 145 pg/ml and pentagastrin-stimulated calcitonin between 10 and 205 pg/ml. In these patients, since medullary carcinoma cannot be completely excluded, total thyroidectomy should be recommended.