What is a calcitonin test?

A calcitonin test measures the level of calcitonin in a sample of your blood. Calcitonin is a hormone that helps control the level of calcium in your blood. Calcitonin is made in your thyroid gland by cells called "C cells." Your thyroid is a small, butterfly-shaped gland in your neck.

Normally, you have a small amount of calcitonin in your blood. But if you have too much, it may be a sign of:

• Medullary thyroid cancer (MTC), a rare cancer that happens when C cells in your thyroid grow out of control. C cells grow in the inside part of your thyroid, which is called the medulla.
• C-cell hyperplasia, a rare condition that causes abnormal growth of C cells in your thyroid. C-cell hyperplasia can turn into medullary thyroid carcinoma.

Your health care provider may order a calcitonin test if you have symptoms of these conditions or if they run in your family.

Other names: thyrocalcitonin, CT, human calcitonin, hCT

What is it used for?

A calcitonin test is most often used to:

• Help diagnose C-cell hyperplasia and medullary thyroid cancer in people who have symptoms
• Find out if treatment for medullary thyroid cancer is working
• Check whether medullary thyroid cancer has returned after treatment
• Screen people who have a high risk of medullary thyroid cancer. The risk is high for people who have a family history of a rare genetic disorder called multiple endocrine neoplasia type 2 (MEN 2).

There are different types of MEN 2 that often cause tumors in certain glands that make hormones, including your thyroid. All types of MEN 2 increase your risk of medullary thyroid cancer. MEN 2 is caused by changes in a gene called RET. Changes in genes are also called gene variants or mutations.

You can inherit MEN 2 - and an increased risk for medullary thyroid cancer - if either of your parents passed a changed RET gene down to you. If MEN 2 runs in your family, regular calcitonin tests can help find cancer early when it may be easier to treat.

Why do I need a calcitonin test?

You may need a calcitonin test to help check for medullary thyroid cancer or C-cell hyperplasia if:

• You have symptoms of either condition which may include:
  • A lump in the front of your neck
  • Swollen lymph nodes in your neck (also called "swollen glands")
  • Pain in your throat
  • Trouble swallowing or breathing
  • A change in your voice, such as hoarseness
  • A long-lasting cough when you don't have a cold
  • Diarrhea
• You have symptoms of multiple endocrine neoplasia type 2 (MEN 2). MEN 2 can affect your thyroid, adrenal, and parathyroid glands. Symptoms depend on which glands are affected. They may include:
  • Fatigue
  • Depression
  • Aches and pains in bones and joints
  • Nausea and vomiting
  • Increased thirst and urination (peeing)
  • High blood pressure
  • Headaches
  • Arrythmia (a problem with the rate or rhythm of your heart)
  • Sweating
• You have a family history of MEN 2, which increases your risk of developing medullary thyroid cancer. If MEN 2 runs in your family, you and your family members, including children, may need regular calcitonin tests to help find cancer before you have symptoms. Your provider may also suggest a blood test to check for changes in your RET genes that cause MEN 2.

If you've been diagnosed with medullary thyroid cancer, you'll need calcitonin testing to:

• Find out how well your treatment is working.
• Check whether the cancer has come back after you finish treatment.

What happens during a calcitonin test?

A health care professional will take a blood sample from a vein in your arm, using a small needle. After the needle is inserted, a small amount of blood will be collected into a test tube or vial. You may feel a little sting when the needle goes in or out. This usually takes less than five minutes.

Will I need to do anything to prepare for the test?

You may need to fast (not eat or drink) for several hours before the test. Your provider will let you know if you need to fast and if there are any special instructions to follow.

Are there any risks to the test?

There is very little risk to having a blood test. You may have slight pain or bruising at the spot where the needle was put in, but most symptoms go away quickly.

What do the results mean?

The meaning of your calcitonin test results depends on the reason you were tested. If you had a calcitonin test:

To help diagnose or screen for medullary thyroid cancer or C-cell hyperplasia:

• A normal calcitonin level may mean that you don't have either condition, but it doesn't rule them out. That's because medullary thyroid cancer and C-cell hyperplasia don't always cause high calcitonin. Your provider may order other tests to learn more.
• A high calcitonin level means that the C cells in your thyroid are making too much calcitonin. The higher the level, the more likely it is that you have medullary thyroid cancer or C-cell hyperplasia. But high calcitonin levels may be caused by other conditions, including certain other cancers, certain medicines, and pregnancy. To make a diagnosis, your provider will consider other information, including other test results.
• A low calcitonin level is not known to be a medical problem.

To monitor treatment for medullary thyroid cancer or to check whether cancer has come back after treatment: The meaning of your test results depends on the type of treatment you're having or had. Treatment usually starts with surgery to remove your thyroid gland. Other treatments include radiation therapy, chemotherapy, and/or medicines.

In general:

• Calcitonin levels that decrease and stay low over time usually mean that your treatment is helping.
• A calcitonin level that decreases but is still higher than normal may mean that you still have some cancer tissue left in your body. You may need more tests and treatment.
• A calcitonin level that increases over time usually means that your cancer has returned or spread to other parts of your body.

Ask your provider to explain what your test results mean for your health.

Learn more about laboratory tests, reference ranges, and understanding results.

Is there anything else I need to know about a calcitonin test?

In certain cases, your provider may order a more accurate type of calcitonin test called a "calcitonin stimulation test." For this test, a sample of your blood will be taken as usual. Then you'll be given medicine to make your body produce calcitonin. The medicine is injected into a vein intravenously (by IV). Afterwards, more blood samples will be taken a few minutes apart. If your calcitonin increases by a lot in each blood sample, it may mean you have C-cell hyperplasia or medullary thyroid carcinoma, but you'll need other tests to find out for sure.