Overview
The Calcitonin Test measures the level of a hormone called calcitonin in the blood.
Calcitonin is produced by the thyroid gland, and its main role is to help control calcium levels in the body.
Doctors usually recommend this test to:
- Diagnose or monitor medullary thyroid carcinoma (MTC) — a rare type of thyroid cancer that produces large amounts of calcitonin.
- Detect C-cell hyperplasia, a condition where thyroid C-cells multiply excessively.
- Assess problems related to calcium regulation and certain neuroendocrine tumors
Where It Is Synthesized or Produced in the Body
- Calcitonin is produced by the C-cells (also called parafollicular cells) in the thyroid gland — located in the front of the neck.
- Smaller amounts of calcitonin are also found in the lungs and intestines.
- Once released into the bloodstream, it helps control calcium and phosphate balance in the body.
Main Functions and Importance
Calcitonin plays an important role in maintaining calcium homeostasis (balance) in the body — though its function is more critical during childhood and bone growth periods.
Main Functions:
- Regulates Calcium and Phosphate Levels:
Calcitonin helps reduce high calcium levels (hypercalcemia) in the blood. - Lowers Blood Calcium by:
- Reducing calcium release from bones (inhibits bone breakdown by osteoclasts).
- Increasing calcium excretion through kidneys.
- Supports Bone Health:
Plays a role in bone formation during childhood and adolescence. - Acts as a Tumor Marker:
In adults, calcitonin is mainly used as a biochemical marker for medullary thyroid carcinoma (MTC) — its level reflects the tumor’s activity and treatment response.
Although calcitonin helps regulate calcium, its absence in adults does not cause major health issues, because parathyroid hormone (PTH) and vitamin D play a much stronger role in calcium balance.
Causes of Low Calcitonin Levels
Low levels of calcitonin are generally considered normal and are not linked to any serious disease in most adults.
Common causes include:
- Normal Physiological Condition:
Healthy adults usually have very low or undetectable calcitonin levels. - After Thyroid Surgery (Thyroidectomy):
Removal of the thyroid gland eliminates calcitonin-producing C-cells. - No Clinical Concern:
Since other hormones maintain calcium balance, low calcitonin rarely causes symptoms.
Symptoms of Low Calcitonin Levels
Usually, there are no symptoms of low calcitonin.
Calcium control in the body remains stable through parathyroid hormone and vitamin D.
Causes of High Calcitonin Levels
Elevated calcitonin levels can be an important warning sign of certain diseases, particularly thyroid-related or neuroendocrine conditions.
Common Causes Include:
- Medullary Thyroid Carcinoma (MTC):
- The most important cause of high calcitonin.
- This rare thyroid cancer arises from C-cells and secretes excess calcitonin.
- The calcitonin level often directly correlates with tumor size and spread.
- C-Cell Hyperplasia:
- A pre-cancerous condition involving an increase in the number of calcitonin-producing C-cells.
- May be found in family members of patients with MTC.
- Other Neuroendocrine Tumors:
- Certain tumors in the lungs, pancreas, or gastrointestinal tract can produce calcitonin.
- Chronic Kidney Disease (CKD):
- Reduced kidney function can cause mild elevation due to decreased clearance.
- Medications:
- Proton Pump Inhibitors (PPIs) used for acidity and reflux may sometimes raise calcitonin levels.
Symptoms of High Calcitonin Levels
Symptoms usually depend on the underlying disease, especially thyroid-related disorders such as medullary thyroid carcinoma (MTC).
Common Symptoms Include:
- Neck lump or swelling (thyroid nodule).
- Hoarseness of voice.
- Difficulty swallowing or breathing.
- Neck pain or fullness.
- Diarrhea and facial flushing (in advanced MTC).
- Changes in calcium levels – though rare, may cause mild muscle cramps or fatigue.
When high calcitonin is due to MTC, symptoms develop gradually and often require imaging tests or biopsy for confirmation.
Reference Ranges
Normal calcitonin levels vary slightly between laboratories, but typical values are:
| Gender | Normal Range | Interpretation |
|---|---|---|
| Men | < 8.4 pg/mL | Normal |
| Women | < 5.0 pg/mL | Normal |
Elevated Calcitonin: Any value above these limits may suggest an abnormality and requires further evaluation (thyroid ultrasound, fine needle aspiration biopsy, or stimulation test).
Sample Type and Test Method
- Sample Type: Blood sample (serum or plasma).
- Collection Method: A small amount of blood is drawn from a vein in the arm.
- Testing Method: Immunoassay techniques such as ELISA or Chemiluminescence Immunoassay (CLIA) are commonly used.
- Optional Test:
Sometimes a Calcitonin Stimulation Test is performed — the patient is given calcium infusion or pentagastrin injection to check if calcitonin levels rise abnormally, which helps confirm MTC diagnosis.
Test Preparation
- No special fasting is required before the test.
- Avoid taking proton pump inhibitors (PPIs) or calcium supplements before testing (as advised by your doctor).
- If you have thyroid nodules or family history of thyroid cancer, inform your doctor in advance.
- Stay calm during blood collection to prevent temporary stress-related hormonal changes.
When to Consult a Doctor
You should talk to your doctor if you:
- Have a lump or swelling in your neck.
- Experience voice changes, throat pain, or difficulty swallowing.
- Have family history of medullary thyroid carcinoma (MTC) or multiple endocrine neoplasia (MEN type 2).
- Show elevated calcitonin levels in a routine blood test.
If results are high, your doctor may recommend:
- Thyroid ultrasound and fine-needle aspiration biopsy.
- Genetic testing for RET gene mutation (common in hereditary MTC).
- Regular monitoring after thyroid cancer surgery to detect recurrence.
Important Word Explanations
- Calcitonin: A hormone made by the thyroid that helps lower blood calcium levels.
- C-cells (Parafollicular Cells): Special thyroid cells that produce calcitonin.
- Medullary Thyroid Carcinoma (MTC): A rare thyroid cancer that releases large amounts of calcitonin.
- C-Cell Hyperplasia: An abnormal increase in calcitonin-producing cells in the thyroid.
- Stimulation Test: A test to check calcitonin response after giving calcium or pentagastrin.
- Tumor Marker: A substance in the blood that helps detect or monitor cancer.
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