Understanding the Lesser-Known Hormone That Helps Regulate Calcium Levels
When it comes to hormones that regulate calcium in the body, most people have heard of vitamin D or parathyroid hormone (PTH). But there’s another player less famous but still important called calcitonin. Produced by the thyroid gland, calcitonin plays a role in controlling calcium levels in the blood and protecting your bones from breaking down too quickly.
Although not as influential as other calcium-regulating hormones, calcitonin serves as a balancing factor, helping fine-tune the body’s mineral metabolism. In this article, we’ll explore what calcitonin is, where it comes from, what it does, and when it matters most in clinical settings.
What Is Calcitonin?
Calcitonin is a peptide hormone secreted by the C-cells (also known as parafollicular cells) of the thyroid gland, located at the front of the neck. Its main function is to lower calcium levels in the blood (hypocalcemic effect) when they become too high.
Calcitonin works as part of a system that includes parathyroid hormone (PTH) and vitamin D, which together help maintain calcium homeostasis, a delicate balance that ensures your muscles contract properly, your nerves transmit signals, and your bones remain strong.
While PTH and vitamin D increase blood calcium levels when needed, calcitonin does the opposite: it reduces calcium levels, helping prevent the harmful effects of excess calcium in the bloodstream.
How Does Calcitonin Work?
Calcitonin acts primarily on bones and kidneys to help regulate calcium:
- In bones, it inhibits the activity of osteoclasts, the cells responsible for breaking down bone tissue. By doing so, it reduces the release of calcium into the bloodstream.
- In the kidneys, calcitonin helps the body excrete more calcium and phosphate in urine, further contributing to a reduction in blood calcium levels.
Together, these effects serve to counteract the actions of PTH during times when calcium levels rise too high such as after a meal rich in calcium or during certain disease states.
Interestingly, in healthy adults, calcitonin is not essential for day-to-day calcium balance, as the body relies more heavily on PTH and vitamin D. However, it becomes important in certain clinical situations or when calcitonin levels are abnormal.
When Is Calcitonin Clinically Important?
Although calcitonin isn’t typically used to regulate everyday calcium fluctuations, it plays a significant role in specific medical conditions and diagnostic procedures:
1. Medullary Thyroid Carcinoma (MTC)
Calcitonin is produced in excess by medullary thyroid cancer, a rare type of thyroid cancer arising from C-cells. In these cases, calcitonin levels are used as a tumor marker to diagnose, monitor, and follow up treatment response.
2. Paget’s Disease of Bone
This chronic condition involves abnormal bone turnover. Calcitonin can be used therapeutically to slow down bone breakdown, although newer medications have largely replaced it.
3. Osteoporosis
In some postmenopausal women, synthetic calcitonin (as a nasal spray or injection) may be prescribed to reduce bone loss. It’s generally considered a second-line treatment but may help with pain relief in acute vertebral fractures.
4. Hypercalcemia (High Blood Calcium)
Calcitonin is occasionally used in hospitals to quickly reduce dangerously high calcium levels, often in combination with other therapies.
What Happens When Calcitonin Levels Are Too High?
High calcitonin levels are uncommon and usually not a cause for concern unless they are very elevated or persistent. In such cases, it may be a sign of:
- Medullary thyroid carcinoma (most common reason for high calcitonin)
- C-cell hyperplasia (a precancerous condition)
- Neuroendocrine tumors in other parts of the body (rare)
- Certain lung diseases or kidney failure (mild elevations)
- Use of certain drugs, such as proton pump inhibitors or calcium supplements
Because calcitonin is used as a tumor marker, elevated levels often prompt further investigation through imaging or biopsy, especially if medullary thyroid carcinoma is suspected.
What Happens When Calcitonin Levels Are Low?
Unlike many hormones, low calcitonin levels rarely cause symptoms or clinical issues. In fact, most people can live without it entirely, especially if the thyroid gland has been removed. The body relies mainly on PTH and vitamin D to regulate calcium levels in the absence of calcitonin.
However, in research and endocrinology, tracking abnormally low calcitonin may be relevant when evaluating certain thyroid conditions or after treatment for medullary thyroid carcinoma.
How Is Calcitonin Measured?
Calcitonin is measured through a fasting blood test, often when thyroid nodules are discovered or if there is a family history of multiple endocrine neoplasia type 2 (MEN2) a genetic condition that includes a high risk of medullary thyroid cancer.
In some cases, doctors may perform a calcitonin stimulation test, using calcium or pentagastrin to provoke hormone release and assess abnormal responses.
Can You Boost or Lower Calcitonin Naturally?
There is no specific dietary or lifestyle intervention proven to significantly increase or decrease calcitonin levels in healthy individuals. However:
- Calcium-rich meals may trigger temporary increases
- Estrogen therapy and certain medications can influence calcitonin
- Chronic kidney disease or hormone-producing tumors may alter its baseline levels
Calcitonin-based medications, such as salmon calcitonin, are available by prescription but are only used under medical supervision for specific conditions.
A Hormone of Balance And a Window into Thyroid Health
Though calcitonin may not make headlines like insulin or cortisol, it quietly contributes to the delicate orchestration of calcium regulation, helping protect bone density and prevent excessive calcium in the bloodstream. More importantly, abnormal calcitonin levels can be early warning signs of serious thyroid conditions, particularly medullary thyroid cancer.
At Erdem Hospital, our endocrinology team offers advanced hormonal testing and personalized care for thyroid disorders, bone health, and calcium metabolism guided by over 37 years of clinical expertise.
So while calcitonin may not demand attention daily, knowing when and how it acts can offer a powerful tool for both prevention and diagnosis in modern medicine.