Calcitonin

Women: below 6.4 ng/L · Men: below 9.5 ng/L

UK labs print a lower cut-off for women than men (for example below 6.4 and below 9.5 ng/L), and the cut-off differs between assays and in children.

Calcitonin is a hormone made by a small group of cells in the thyroid called C cells. It has a minor role in calcium balance. Its main use as a blood test is as a marker for the C cells themselves, which can multiply in a rare thyroid cancer called medullary thyroid cancer.

It is requested when a thyroid nodule is being looked into, in families with inherited endocrine tumour conditions, and for follow-up after treatment of medullary thyroid cancer. It is not part of routine thyroid testing.

• Medullary thyroid cancer and the C-cell overgrowth that precedes it
• Long-term kidney disease
• Acid-lowering medicines of the proton pump inhibitor class
• Other tumours, including some lung and pancreatic tumours
• Smoking, male sex and heavier body weight, in the general population
• Autoimmune thyroid disease, slightly

• A value below the cut-off is the expected finding
• After complete removal of medullary thyroid cancer the expected level is undetectable
• Older age, in the general population

• Acid-lowering medicines and kidney disease raise it without any thyroid problem
• Smokers and men run higher in the general population
• Some antibodies in the blood interfere on certain analysers

Usually a morning sample. The specimen is often separated and frozen quickly, so it may be sent to a specialist laboratory. Repeat testing and, where needed, a stimulation test are done in specialist clinics.

Written by a UK consultant physician. Typical UK adult reference ranges; your laboratory's own printed range takes precedence.