What is calcitonin?
Calcitonin is a hormone that your thyroid gland makes and releases to help regulate calcium levels in your blood by decreasing it. Calcitonin opposes the actions of the parathyroid hormone, which is a hormone that increases your blood calcium levels.
Your thyroid is a small, butterfly-shaped gland located at the front of your neck under your skin. It’s a part of your endocrine system and controls many of your body’s important functions by producing and releasing (secreting) certain hormones. The C-cells in your thyroid (parafollicular cells) make and secrete calcitonin.
Hormones are chemicals that coordinate different functions in your body by carrying messages through your blood to your organs, muscles and other tissues. These signals tell your body what to do and when to do it.
Calcitonin is a unique hormone because healthcare providers and scientists don’t fully understand its importance. While they know what it does, they don’t understand why we have it because irregular calcitonin levels cause few or no symptoms.
Calcitonin as medicine
In the past, healthcare providers prescribed synthetic (manufactured) forms of calcitonin as medicine to treat Paget’s disease of the bone, hypercalcemia and osteoporosis. However, with the introduction of newer drugs, such as bisphosphonates, providers seldom use this form of calcitonin for treatment.
What is calcium and what does it do?
Calcium is one of the most important and common minerals in your body. Your body stores most of your calcium in your bones, but you have and need it in your blood as well. The calcium in your blood has many important roles, including:
- Helping your nerves work.
- Helping to make your muscles squeeze together (contract) so you can move.
- Helping your blood clot if you’re bleeding.
- Helping your heart work properly.
What is the function of calcitonin?
Calcitonin’s main job is to lower calcium levels in your blood (not your bones). It does this in two main ways:
- Calcitonin inhibits (blocks) the activity of osteoclasts, which are cells that break down bone. When osteoclasts break down your bone, the calcium from your bone is released into your bloodstream. Therefore, the temporary blocking of osteoclasts by calcitonin reduces the amount of calcium that enters your blood.
- Calcitonin can decrease the amount of calcium that your kidneys reabsorb and release back into your bloodstream, thus causing lower blood calcium levels.
What stimulates calcitonin release?
Your thyroid releases calcitonin based on the level of calcium in your blood. When your blood calcium levels increase, your thyroid releases calcitonin in higher quantities. When blood calcium levels decrease, your thyroid decreases the amount of calcitonin it releases.
What’s the difference between parathyroid hormone and calcitonin?
Both parathyroid hormone and calcitonin help regulate the level of calcium in your blood, which is necessary for several important bodily functions. The difference is how they do so and how much they affect your calcium levels.
Parathyroid hormone (PTH) is a hormone that your parathyroid glands make and release to control the level of calcium in your blood by increasing it. PTH also helps control the levels of phosphorus (a mineral) and vitamin D (a hormone) in your blood and bones. You have four pea-sized parathyroid glands located behind your thyroid gland.
Whereas parathyroid hormone increases blood calcium levels, calcitonin decreases blood calcium levels. However, PTH seems to have a more important role in regulating your blood calcium levels than calcitonin. Scientists mainly know this because having high or low levels of PTH can cause hypercalcemia (high blood calcium levels) or hypocalcemia (low blood calcium levels), respectively, which can be serious conditions. On the other hand, having high or low levels of calcitonin doesn’t have much of an effect on your body.
What’s the difference between calcitonin and calcitriol?
While calcitonin and calcitriol are both hormones that affect calcium levels, they have different functions — calcitriol helps increase blood calcium levels, and calcitonin helps decrease blood calcium levels.
Calcitriol, a hormone that’s also known as active vitamin D, helps to increase the amount of calcium your gut can absorb from the food you eat and release it into your bloodstream. Calcitriol also prevents calcium loss from your kidneys. Parathyroid hormone is responsible for stimulating the enzyme that transforms vitamin D your skin makes from sun exposure into calcitriol.
Calcitonin decreases calcium levels by blocking the breakdown of bone calcium and by preventing your kidneys from reabsorbing calcium. In other words, it encourages calcium loss through your kidneys.
What test measures calcitonin levels?
Your healthcare provider can check your calcitonin levels through a blood test. It involves using a needle to draw a blood sample from a vein in your arm.
Since abnormal calcitonin levels don’t cause symptoms in and of themselves, providers typically only order a calcitonin blood test for the following reasons:
- To help diagnose medullary thyroid cancer (MTC) or C-cell hyperplasia.
- To monitor the treatment of MTC.
- If you have a family history of multiple endocrine neoplasia (MEN) type 2, an inherited condition that’s associated with three primary types of endocrine tumors, including MTC.
What are normal calcitonin levels?
Normal ranges for calcitonin levels can vary from lab to lab. Always reference the lab’s normal range on your blood test report.
In general, the normal ranges for calcitonin include:
- For people assigned male at birth: 0 to 7.5 pg/mL (picograms per milliliter).
- For people assigned female at birth: 0 to 5.1 pg/mL.
A picogram is one-trillionth of a gram.
If you need to get a calcitonin level test, your healthcare provider will interpret your results and let you know if you need to get further testing.
What happens when calcitonin levels are too high?
Having a higher-than-normal level of calcitonin doesn’t seem to negatively affect your body or cause symptoms.
However, having high levels of calcitonin may be a sign of two rare conditions, including:
- Medullary thyroid cancer (MTC): This is a rare thyroid cancer that originates in the C-cells of your thyroid gland — the cells that make calcitonin. Because of this, medullary thyroid cancer can cause those cells to make excess amounts of calcitonin. While the excess calcitonin doesn’t affect your body, MTC can, and frequently does, spread to other tissues (metastasizes), especially lymph nodes.
- C-cell hyperplasia: This is a benign (noncancerous) condition that causes abnormal growth of C-cells in your thyroid. The enlarged tissue can release excess calcitonin. C-cell hyperplasia can sometimes progress to become medullary thyroid cancer (MTC).
Again, while high levels of calcitonin aren’t harmful, they can indicate MTC or C-cell hyperplasia. If you’re experiencing symptoms of either of these two conditions, such as a lump in the front of your neck or trouble swallowing, your provider may order a calcitonin test to help diagnose or rule out these two conditions.
What happens when calcitonin levels are too low?
There doesn’t seem to be any effect on your body as a result of having too little calcitonin. People who have had their thyroid gland removed and have undetectable levels of calcitonin have no negative signs or symptoms related to blood calcium levels. (People who have had their thyroid removed do, however, usually need to take a life-long synthetic form of thyroid hormone — the main hormone your thyroid releases.)
A note from Cleveland Clinic
Calcitonin is a bit of a mysterious hormone. While having lower- or higher-than-normal levels doesn’t seem to cause any negative effects, high levels of calcitonin can be a sign of medullary thyroid cancer or C-cell hyperplasia. If you’re experiencing symptoms of either of these conditions or have questions about your risk of getting them, contact your healthcare provider. They’re there to help you.
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