Specimen Information

Type

Gold, SST

Volume

2.0 ml

Transport Info

Centrifuge and immediately transfer serum to separate plastic tube
Refrigerated

Fasting Required?

False

Clinical Significance

Measurement of serum calcitonin is considered a reliable method for confirming diagnosis of MTC (medullary thyroid carcinoma).

Calcitonin is secreted by the parafollicular C-cells of the thyroid gland. Its primary physiological effect is to lower serum calcium levels. It does this, in part, by inhibiting bone resorption and by promoting urinary clearance of calcium. Elevated levels of calcitonin (greater than 100 pg/mL) may be encountered in a variety of pathological conditions including leukemias and myeloproliferative disorders. The most notable condition expressing elevated calcitonin levels is medullary thyroid carcinoma (MTC). The measurement of serum calcitonin is considered to be a reliable method for confirming the diagnosis of MTC. Calcitonin levels may be elevated before there is any clinical evidence of a tumor. In patients with serum calcitonin levels that are not clearly diagnostic, stimulation of calcitonin by provocative testing (calcium) will usually support the diagnosis of MTC. Serum calcitonin and chorioembryonic antigen (CEA) should be measured six months after surgery to detect the presence of residual tumor. It is recommended that those patients with a basal serum calcitonin concentration below 10 pg/mL should undergo calcium stimulation testing. MTC can occur as an inherited malignancy; therefore, the determination of calcitonin levels in family members of patients with MTC serves as a valuable screening tool. In this type of screening, one of the provocative tests is often performed. Following treatment of MTC by total thyroidectomy, the evaluation of calcitonin levels with or without stimulation tests can provide information concerning residual or recurrent disease that is not clinically apparent.