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  Back Blood-tests Explained


Calcitonin


At a Glance

Why Get Tested?

To help diagnose and monitor C-cell hyperplasia and medullary thyroid cancer; to screen those at risk for multiple endocrine neoplasia type 2 (MEN 2)

When to Get Tested?

When a healthcare practitioner suspects that you have or when you are being treated for medullary thyroid cancer, or when a family member has medullary thyroid cancer or MEN 2

Sample Required?

A blood sample drawn from a vein in your arm

Test Preparation Needed?

Overnight fasting may be required; follow instructions provided by your healthcare practitioner or the laboratory.

The Test Sample

What is being tested?

Location of the thyroidCalcitonin is a hormone produced by special cells in the thyroid called C-cells. The thyroid is a small butterfly-shaped gland that lies over and flat against the windpipe in the throat. It produces calcitonin and several hormones that help control the rate of metabolism, primarily thyroxine (T4) and triiodothyronine (T3). This test measures the amount of calcitonin in the blood.

Calcitonin is involved in the regulation of calcium levels in the blood through inhibiting bone breakdown (resorption) and decreasing kidney reabsorption of calcium. However, its role in calcium regulation is minor compared with parathyroid hormone (PTH) and 1,25-dihydroxyvitamin D. Thus, the measurement of calcitonin in blood is not useful for diagnosis of disorders of calcium regulation.

In two rare conditions, C-cell hyperplasia and medullary thyroid cancer, excessive amounts of calcitonin are produced. C-cell hyperplasia is a benign condition that 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 1-2% of all thyroid cancers in the United States. About 75-80% of medullary thyroid cancer cases are sporadic, occurring in those who do not have a family history of the disease. About 20-25% of cases are related to an inherited 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 altered RET gene is inherited in an autosomal dominant fashion. Only one copy of the mutated gene – from either a father or mother – is required to have a greatly increased risk of developing medullary thyroid cancer. Most cases of sporadic medullary thyroid cancer develop when people are in their 40s or 50s, and the prevalence is higher in women. The inherited form affects both sexes equally and can occur at an earlier age.

How is the sample collected for testing?

A blood sample is obtained by inserting a needle into a vein in the arm.

Is any test preparation needed to ensure the quality of the sample?

Overnight fasting may be required. Follow the instructions provided by your healthcare practitioner or the laboratory.

The Test

How is it used?

The calcitonin test is primarily used to help diagnose C-cell hyperplasia and medullary thyroid cancer, to evaluate the effectiveness of treatment, and to monitor those affected for recurrence. It is also ordered to screen for medullary thyroid cancer in family members of people with multiple endocrine neoplasia type 2 (MEN 2).

C-cell hyperplasia and medullary thyroid cancer are two rare conditions in which excessive amounts of calcitonin are produced. C-cell hyperplasia is a benign condition that 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. (See the "What is being tested?" section for more information about these conditions.)

Stimulation tests are more sensitive than calcitonin measurements alone. This involves collecting a baseline sample, then giving a person an injection of intravenous calcium or pentagastrin to stimulate calcitonin production. Several more blood samples are then collected over the next few minutes to measure the effect of the stimulation. People with early C-cell hyperplasia and/or medullary thyroid cancer will usually have very significant increases in their levels of calcitonin during this test.

When is it ordered?

Calcitonin levels may be ordered when someone is suspected of having C-cell hyperplasia or medullary thyroid cancer. A person may experience signs and symptoms, such as:

  • A lump or swelling at the front of the neck
  • Pain at the throat or front of the neck
  • A change in the voice, hoarseness
  • Difficulty swallowing or breathing
  • Persistent cough not associated with a cold

A recent study also recommended measuring calcitonin before surgery in all people with thyroid nodules, but not all clinicians agree. Stimulation tests may be ordered when someone has indeterminate or normal calcitonin results but clinical suspicions remain.

Calcitonin tests may be periodically performed on 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 someone has 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?

A low level of calcitonin means that it is unlikely that symptoms are due to C-cell hyperplasia or medullary thyroid cancer.

An elevated concentration of calcitonin means that excessive amounts are being produced. Significantly elevated levels of calcitonin are a good indicator of C-cell hyperplasia or medullary thyroid cancer; however, the 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 removal of 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 means that some calcitonin-producing tissue remains. Healthcare practitioners will monitor calcitonin and watch for increases over time. If calcitonin levels begin to rise, then it is likely that there is a recurrence of medullary thyroid cancer.

Is there anything else I should know?

With medullary thyroid cancer and C-cell hyperplasia, other thyroid tests, such as T4, T3, and TSH, are usually normal while calcitonin levels are elevated.

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).

Concentrations of calcitonin 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.

Other conditions with elevated calcitonin include:

  • Intestinal, gastric, or bronchial carcinoid tumors
  • Chronic renal failure
  • Zollinger-Ellison syndrome
  • Pernicious anemia


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