Calcitonin
Also known as: hCT
What Does Calcitonin Measure?
Calcitonin is a hormone produced primarily by the parafollicular C cells (also called C cells) of the thyroid gland. A blood test measuring calcitonin quantifies the concentration of this hormone circulating in the bloodstream, typically expressed in picograms per milliliter (pg/mL) or nanograms per liter (ng/L). The test reflects how actively the thyroid's C cells are producing and secreting this hormone, which plays a central role in calcium and bone metabolism by opposing the effects of parathyroid hormone (PTH).
Why Does Calcitonin Matter?
Calcitonin is most clinically significant as a tumor marker for medullary thyroid carcinoma (MTC), a cancer that arises directly from the C cells. Elevated calcitonin levels can indicate MTC or its precursor condition, C-cell hyperplasia, making it a critical screening and monitoring tool. Beyond cancer surveillance, calcitonin helps regulate calcium homeostasis by inhibiting bone resorption and reducing calcium reabsorption in the kidneys, so abnormal levels may also provide insight into disorders of calcium and bone metabolism. Regular monitoring is essential for patients with a family history of MTC or Multiple Endocrine Neoplasia type 2 (MEN2) syndrome.
Normal Ranges
Males
< 18.2 pg/mL (some labs use < 11.5 pg/mL)
Females
< 11.5 pg/mL (some labs use < 5.0 pg/mL)
Children
Varies by age; neonates may have higher values (up to 40 pg/mL), declining to adult ranges by adolescence
Causes of High Levels
- Medullary thyroid carcinoma (MTC) — the most common and significant cause of markedly elevated calcitonin
- C-cell hyperplasia — a precancerous proliferation of thyroid C cells, often seen in MEN2 syndrome
- Multiple Endocrine Neoplasia type 2 (MEN2) — a hereditary syndrome causing tumors in multiple endocrine glands
- Hypercalcemia — elevated blood calcium can stimulate calcitonin secretion as a compensatory response
- Chronic kidney disease — impaired renal clearance can lead to accumulation of calcitonin in the bloodstream
- Other neuroendocrine tumors — carcinoid tumors, small cell lung cancer, and pheochromocytoma can occasionally produce ectopic calcitonin
Causes of Low Levels
- Surgical removal of the thyroid (thyroidectomy) — eliminates the primary source of calcitonin production
- Hypoparathyroidism with hypocalcemia — chronically low calcium reduces the stimulus for calcitonin secretion
How to Improve Your Calcitonin
Diet
- Maintain adequate calcium intake (1,000–1,200 mg/day from dairy, leafy greens, or fortified foods) to support normal calcitonin regulation
- Eat foods rich in vitamin D such as fatty fish (salmon, mackerel), egg yolks, and fortified milk to optimize calcium-calcitonin axis function
- Limit excessive alcohol consumption, as alcohol can disrupt calcium metabolism and affect calcitonin signaling
- Include magnesium-rich foods like nuts, seeds, and whole grains, as magnesium supports overall mineral homeostasis
- Reduce high-sodium foods, since excess sodium increases urinary calcium loss and can disrupt calcium-calcitonin balance
Supplements
- Vitamin D3 (1,000–2,000 IU/day) to support calcium absorption and normal endocrine function — consult a doctor for dosing
- Calcium carbonate or calcium citrate (500–1,000 mg/day in divided doses) if dietary intake is insufficient
- Magnesium glycinate or citrate (200–400 mg/day) to support bone mineral metabolism
- Omega-3 fatty acids (1,000–2,000 mg/day of EPA/DHA) for general anti-inflammatory support of thyroid health
Related Biomarkers
Frequently Asked Questions
What does a high calcitonin level mean?
A significantly elevated calcitonin level is most commonly associated with medullary thyroid carcinoma (MTC), a type of thyroid cancer originating in the C cells. However, mildly elevated levels can also occur with C-cell hyperplasia, other neuroendocrine tumors, kidney disease, or even after certain medications. Any elevated result should be investigated with imaging, genetic testing, and specialist referral to rule out cancer.
Is a calcitonin test the same as a thyroid function test?
No, they are different tests. Standard thyroid function tests measure hormones like TSH, free T3, and free T4, which are produced by the main thyroid follicular cells and regulate metabolism. Calcitonin is produced by a distinct cell type (C cells) in the thyroid and is primarily used as a tumor marker for medullary thyroid carcinoma, not to assess general thyroid hormone function.
Should calcitonin be checked routinely before thyroid surgery?
Many endocrinology guidelines recommend measuring calcitonin levels in patients with thyroid nodules before surgery, as it can detect unsuspected medullary thyroid carcinoma in a small but significant percentage of cases. However, this remains a topic of some debate, and practices vary by country and institution. Discussing this with your endocrinologist or surgeon is advisable, especially if you have a family history of MTC.
Can medications affect calcitonin levels?
Yes, certain medications can influence calcitonin levels. Proton pump inhibitors (PPIs), glucocorticoids, and some calcium-affecting drugs may alter results. Additionally, synthetic calcitonin (salmon calcitonin) is used therapeutically for conditions like osteoporosis and Paget's disease. Informing your doctor about all medications and supplements before testing is important for accurate interpretation.