What is being tested?
Calcitonin is a hormone that helps regulate how the body uses calcium. It is produced by special cells in the thyroid called C-cells. The thyroid is a small butterfly-shaped gland located at the base of the neck. Besides calcitonin, the thyroid produces other hormones, primarily thyroxine (T4) and some triiodothyronine (T3), that help control the rate of metabolism.
In two rare conditions, C-cell hyperplasia and medullary thyroid cancer (MTC), excess amounts of calcitonin are produced. The calcitonin test measures the level in the blood and may be used to detect and monitor these conditions.
- C-cell hyperplasia is a benign condition that causes abnormal growth of cells in the thyroid. It may or may not progress to become medullary thyroid cancer.
- Medullary thyroid cancer is malignant – it can spread beyond the thyroid and can be difficult to treat if it is not discovered early.
Medullary cancer is a rare form of thyroid cancer that accounts for about 4% of all thyroid cancers in the United States. Approximately 52,000 people are diagnosed with thyroid cancer each year, and about 2,000 people die of the disease.
About 75% of medullary thyroid cancer cases are sporadic, occurring in people who do not have a family history of the disease. Most sporadic cases develop when people are in their 40s or 50s and are more common in women than men.
Up to 25% of cases of MTC are related to an inherited variant (mutation) in the RET gene that leads to multiple endocrine neoplasia type 2 (MEN 2). MEN 2 is a syndrome associated with several related diseases, including medullary thyroid cancer and pheochromocytomas. The RET gene variant is inherited in an autosomal dominant fashion. This means you only need to inherit one copy of the gene variant from either your father or mother to have a greatly increased risk of developing medullary thyroid cancer. This inherited form affects both men and women equally and can occur at a younger age.
How is the test used?
The calcitonin test is primarily used to help diagnose C-cell hyperplasia and medullary thyroid cancer, to help determine whether treatment has been effective, and to monitor for recurrence of thyroid cancer. Testing may be used to help detect medullary thyroid cancer in family members of people with multiple endocrine neoplasia type 2 (MEN 2).
A stimulation test is more sensitive than a single calcitonin measurement. This procedure involves collecting an initial blood sample (baseline), then giving an injection of intravenous calcium or pentagastrin, substances that stimulate the thyroid to produce calcitonin. Several more blood samples are collected over the next several minutes to measure the effect of the stimulation.
When is it ordered?
Calcitonin levels may be ordered when it is suspected that you have C-cell hyperplasia or medullary thyroid cancer. These conditions may be suspected when you have signs and symptoms, such as:
- A lump or swelling at the front of your neck
- Pain in your throat or front of your neck
- A change in your voice, hoarseness
- Difficulty swallowing or breathing
- Persistent cough not associated with a cold
Calcitonin tests may be ordered periodically for family members of those who have MEN 2, starting at an early age, in order to detect medullary thyroid cancer or C-cell hyperplasia as early as possible.
When you have been treated for medullary thyroid cancer, calcitonin testing will usually be ordered at regular intervals to monitor treatment effectiveness and recurrence.
What does the test result mean?
Calcitonin levels are normally low. However, a low result does not rule out medullary thyroid cancer (MTC). While most people with sporadic MTC have high calcitonin levels, about 30% of people with familial MTC or MEN 2 have normal levels.
An elevated level of calcitonin means that excess amounts are being produced. Significantly elevated levels of calcitonin (e.g., greater than 20 times the upper limit) are a good indicator of C-cell hyperplasia or medullary thyroid cancer. Likewise, if you have early C-cell hyperplasia or medullary thyroid cancer, you will usually have very significant increases in your levels of calcitonin during a calcitonin stimulation test. However, your healthcare practitioner will use other procedures, such as a thyroid biopsy, scan, and ultrasound, to establish the diagnosis.
With successful treatment for medullary thyroid cancer, which may involve surgery to remove the thyroid gland and often some surrounding tissues, calcitonin levels will usually fall to very low levels. If the values stay low over time, then it is likely that the treatment was effective.
In some cases, calcitonin levels will fall but remain moderately elevated after treatment. This may mean that some tissue that produces calcitonin remains. Healthcare practitioners will monitor calcitonin and watch for increases over time. If calcitonin levels begin to rise, then it is likely that medullary thyroid cancer has returned.
Are calcitonin levels elevated in other conditions besides c-cell hyperplasia and medullary thyroid cancer?
Yes. Calcitonin levels may be elevated with lung, breast, and pancreatic cancers, insulinomas, and rare pancreatic tumors called VIPomas (associated with vasoactive intestinal peptide (VIP) hormone production).
Other conditions with elevated calcitonin include:
- Intestinal, gastric, or bronchial carcinoid tumors
- Chronic renal failure
- Zollinger-Ellison syndrome
- Pernicious anemia
Why isn’t calcitonin testing performed as a routine screen?
C-cell hyperplasia and medullary thyroid cancer are both sufficiently rare that it is not useful to screen for calcitonin in the general population.
If my thyroid is removed, will I need to replace my calcitonin?
No, the body can function without it. However, you will need lifelong thyroid hormone (usually T4) replacement therapy. This is manufactured thyroid hormone taken as a pill by mouth that replaces your body’s own thyroid hormone.
Is calcitonin ever used as a supplement?
Yes, but in a totally different context. Because it inhibits bone breakdown (resorption) when given in very large doses, calcitonin is sometimes given as a drug to people who have osteoporosis. It helps maintain bone density and has a pain-relieving effect on bone. The supplement is usually administered as an injection or nasal spray. Calcitonin is a protein and will be broken down by digestion, becoming inactive, so it cannot be taken by mouth.
Is there anything else I should know?
With medullary thyroid cancer and C-cell hyperplasia, other thyroid tests, such as T4, T3, and thyroid stimulating hormone (TSH), are usually normal while calcitonin levels are elevated.
Calcitonin levels may be increased with use of drugs such as epinephrine, glucagon, and oral contraceptives, and are normally higher in newborns as well as in women during pregnancy.