Overview
The Calcitonin Test measures the level of a hormone called calcitonin in the blood. Calcitonin is produced by specific cells in the thyroid gland and plays a supporting role in calcium regulation.
In clinical practice, this test is most often used not for routine calcium assessment, but as a marker of thyroid C-cell activity. Doctors commonly request it to help detect or monitor medullary thyroid carcinoma (MTC), a rare thyroid cancer that releases calcitonin into the bloodstream. It may also be used when C-cell hyperplasia or certain neuroendocrine conditions are being considered.
Where It Is Synthesized or Produced in the Body
Calcitonin is produced mainly by C-cells (parafollicular cells) of the thyroid gland, which sits at the front of the neck. Smaller amounts may be produced in tissues such as the lungs and gastrointestinal tract, but these are usually not clinically significant.
After release, calcitonin circulates in the blood and participates in calcium and phosphate balance, acting as a counter-regulatory hormone to calcium-raising mechanisms.
Main Functions and Importance
Calcitonin has a modest but well-defined physiological role, particularly earlier in life.
Its main clinical and biological roles include:
Regulation of Calcium Levels
Calcitonin helps reduce elevated blood calcium levels by limiting calcium release from bones and promoting calcium excretion through the kidneys.
Bone Metabolism Support
Its effects are more pronounced during childhood, adolescence, and periods of bone growth.
Tumor Marker in Adults
In adult medicine, calcitonin’s greatest importance is as a biochemical marker. Persistently elevated levels strongly suggest abnormal C-cell activity and are closely linked to medullary thyroid carcinoma.
In everyday clinical experience, calcium balance in adults is primarily maintained by parathyroid hormone and vitamin D, which is why low calcitonin levels are usually not a concern.
Causes of Low Calcitonin Levels
Low or undetectable calcitonin levels are common and generally considered normal.
Typical reasons include:
- Normal adult physiology, where calcitonin secretion is minimal
- After thyroid surgery, when C-cells have been removed
- No pathological significance, as calcium control remains intact through other hormones
Symptoms of Low Calcitonin Levels
There are usually no symptoms associated with low calcitonin levels. The body maintains calcium balance effectively without relying heavily on this hormone.
Causes of High Calcitonin Levels
Elevated calcitonin levels warrant careful evaluation, as they may reflect abnormal thyroid C-cell activity.
Common clinical associations include:
Medullary Thyroid Carcinoma (MTC)
This is the most important cause of markedly elevated calcitonin. Levels often rise in parallel with tumor burden and are used for diagnosis and follow-up.
C-Cell Hyperplasia
An increase in calcitonin-producing cells, sometimes seen in relatives of patients with hereditary MTC.
Other Neuroendocrine Tumors
Certain tumors outside the thyroid may produce calcitonin, though this is less common.
Chronic Kidney Disease
Mild elevations may occur due to reduced clearance.
Medication Effects
Drugs such as proton pump inhibitors can occasionally cause modest increases.
Symptoms of High Calcitonin Levels
Symptoms are related to the underlying condition, not the hormone itself.
They may include:
- A lump or swelling in the neck
- Voice changes or hoarseness
- Difficulty swallowing or breathing
- Neck discomfort or fullness
- Diarrhea or flushing in advanced cases
In many patients, elevated calcitonin is detected before clear physical symptoms appear, which is why the test is valuable in early detection.
Reference Ranges
Reference values vary slightly between laboratories, but typical adult ranges are:
- Men: < 8.4 pg/mL
- Women: < 5.0 pg/mL
Values above these limits are considered abnormal and usually prompt further thyroid evaluation rather than immediate conclusions.
Sample Type and Test Method
- Sample type: Blood (serum or plasma)
- Collection: Venous blood draw from the arm
Modern laboratories use sensitive immunoassay techniques such as chemiluminescence or ELISA to measure calcitonin accurately.
In selected cases, a calcitonin stimulation test may be performed to clarify borderline results.
Test Preparation
- Fasting is usually not required
- Inform your doctor about medications, especially acid-suppressing drugs
- Share any history of thyroid nodules or thyroid cancer in the family
These details help ensure correct interpretation.
When to Consult a Doctor
You should seek medical advice if you:
- Notice a persistent neck lump or swelling
- Have unexplained voice changes or swallowing difficulty
- Have a family history of medullary thyroid carcinoma or MEN type 2
- Receive an elevated calcitonin result on routine testing
Doctors may then recommend imaging, biopsy, genetic testing, or long-term monitoring, depending on the overall clinical picture.
Important Word Explanations
- Calcitonin: A thyroid hormone involved in lowering blood calcium levels.
- C-cells: Specialized thyroid cells that produce calcitonin.
- Medullary Thyroid Carcinoma (MTC): A rare thyroid cancer arising from C-cells.
- C-Cell Hyperplasia: An increased number of calcitonin-producing cells.
- Stimulation Test: A test that assesses calcitonin response after stimulation.
- Tumor Marker: A blood substance used to detect or monitor certain cancers.
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