Calcitonin, Serum

What is Calcitonin?

Calcitonin is a hormone that plays a role in regulating the level of calcium in your blood by decreasing it. 

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.

Where is Calcitonin produced?

Calcitonin is a hormone that is produced in humans by the parafollicular cells (commonly known as C-cells) of the thyroid gland. 

What are the functions of Calcitonin?

Calcitonin is involved in regulating levels of calcium and phosphate in the blood. Its biological function in humans is to have a relatively minor role in calcium balance. It works by opposing the action of parathyroid hormone, which means that it acts to reduce calcium levels in the blood. However, the importance of this role in humans is unclear, as patients who have very low or very high levels of calcitonin show no adverse effects.

The secretion of both calcitonin and parathyroid hormone is determined by the level of calcium in the blood. When levels of calcium in the blood increase, calcitonin is secreted in higher quantities. When levels of calcium in the blood decrease, this causes the amount of calcitonin secreted to decrease too.

The secretion of calcitonin is also inhibited by the hormone somatostatin, which can also be released by the C-cells in the thyroid gland.

Calcitonin reduces calcium levels in the blood by two main mechanisms:

→ It inhibits the activity of osteoclasts, which are the cells responsible for breaking down bone. When bone is broken down, the calcium contained in the bone is released into the bloodstream. Therefore, the inhibition of the osteoclasts by calcitonin directly reduces the amount of calcium released into the blood. However, this inhibition has been shown to be short-lived.

→ It can also decrease the reabsorption of calcium in the kidneys, again leading to lower blood calcium levels.

How about manufactured forms of Calcitonin?

Manufactured forms of calcitonin have, in the past, been given to treat Paget’s disease of bone and sometimes hypercalcaemia and bone pain. However, with the introduction of newer drugs, such as bisphosphonates, their use is now very limited.

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

→ Arrhythmia (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 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.

References:

Felsenfeld AJ, Levine BS. Calcitonin, the forgotten hormone: does it deserve to be forgotten? Clin Kidney J. 2015 Apr;8(2):180-7. doi: 10.1093/ckj/sfv011. Epub 2015 Mar 20. PMID: 25815174; PMCID: PMC4370311.

https://www.yourhormones.info/hormones/calcitonin/