Wallach's Interpretation of Diagnostic Tests: Pathways to Arriving at a Clinical Diagnosis (760 page)

   Calcitonin, also known as thyrocalcitonin, is a polypeptide hormone secreted by parafollicular C cells of thyroid. It acts directly on osteoclasts to decrease bone-resorbing activity and to cause decreased serum calcium.

   
Normal range:

   Older children and adults: <12 pg/mL in males; <5 pg/mL in females

   Infants and young children: <40 pg/mL in children <6 months; <15 pg/mL in children 6 months to 3 years (Basuyau)

   Use

   Serum calcitonin is determined to diagnose recurrence of medullary carcinoma or metastases after the primary tumor has been removed or to confirm complete removal of the tumor if basal calcitonin has been previously increased.

   Measurement of serum calcitonin has not been a part of the routine evaluation of patients with thyroid nodules in the United States. The high frequency of falsely high serum calcitonin values and the accuracy of fine needle aspiration biopsy argue against a change in this recommendation. Furthermore, occasional patients with locoregional metastases or locally invasive medullary thyroid carcinoma (MTC) have normal unstimulated serum calcitonin concentrations.

   Interpretation

Increased Values

   Carcinoma of the lung, breast, islet cell, or ovary and carcinoid due to ectopic production and in myeloproliferative disorders

   Hypercalcemia of any etiology, stimulating calcitonin production

   Zollinger-Ellison syndrome

   C-cell hyperplasia

   Pernicious anemia