A blood test can sometimes raise questions, especially when faced with a calcitonin result. Understanding this marker is essential to correctly interpret your tests without jumping to hasty conclusions. This article aims to provide you with clear and factual information about calcitonin, its role in the body, and the significance of its variations. It will help you better engage with your doctor, who remains your primary contact for any medical questions.

What is Calcitonin?

To fully understand this marker, it’s helpful to define what it is and how it works. Calcitonin is a hormone that plays a precise role in regulating a vital mineral: calcium.

Definition and Primary Role

Calcitonin (CT) is a hormone primarily produced by specialized cells in the thyroid gland, called C cells. The thyroid is a butterfly-shaped gland located at the base of the neck. Once produced, these hormones are released into the bloodstream to act as chemical messengers throughout the body.

The main function of calcitonin is to participate in the regulation of blood calcium levels (calcemia). It acts as a regulator that intervenes when this level becomes too high. It works in tandem with another hormone, parathyroid hormone (PTH), to maintain a stable calcium balance, essential for the proper functioning of nerves, muscles, and bone strength.

How Does Calcitonin Work?

When blood calcium levels rise, the thyroid releases calcitonin. This hormone then acts primarily on two targets to bring calcium levels back to normal. Firstly, it inhibits the activity of osteoclasts, the cells responsible for breaking down bone. By limiting this degradation, it prevents the release of bone calcium into the blood.

Secondly, calcitonin can promote the elimination of excess calcium by the kidneys through urine. Thanks to this dual mechanism, it helps lower excessively high calcium levels and maintain calcium homeostasis.

Why Measure Calcitonin Levels?

Measuring calcitonin levels is not a routine test. It is generally prescribed in specific contexts, primarily related to thyroid health.

The Primary Interest of Measurement: MTC

The most common reason for measuring calcitonin is the detection and monitoring of a rare condition: medullary thyroid carcinoma (MTC). This type of cancer develops from the C cells that produce calcitonin. In cases of MTC, the cancerous cells produce a very large amount of this hormone.

A very high calcitonin level is therefore a very reliable biomarker of this disease. Its measurement allows for diagnosis, sometimes at an early stage. It is also used to monitor patients after MTC treatment to detect any potential recurrence.

The Importance of Medical Follow-up

Detecting an abnormal calcitonin level is important. A very high, unexplained level can be a sign of MTC requiring specialized care. According to data from the American Thyroid Association, the prognosis for MTC is much better when diagnosed at an early stage. This is why an abnormal result should always lead to a medical consultation for further investigation.

Understanding Your Calcitonin Test Results

Your results sheet presents your calcitonin level alongside reference values. Knowing how to read this information is the first step to understanding your test.

Calcitonin Reference Values

Normal calcitonin values are generally very low. They can vary slightly depending on the laboratory and the measurement techniques used. As an indication, the reference ranges are often as follows:

• For men: less than 10 pg/mL (picograms per milliliter)
• For women: less than 5 pg/mL

It is imperative to always compare your result to the reference range indicated on your analysis report, as it is specific to the method used.

How to Interpret Your Results?

To read your results, identify your value and compare it to the laboratory’s norm. A symbol (like a star) or color may indicate a result outside this range. Also note the sample date to track any potential evolution in future tests. However, only a doctor can perform a complete interpretation, taking into account your overall health, your symptoms, and any other examinations.

What are the Causes of a Variation in Calcitonin Levels?

A calcitonin level outside the norms is not systematically linked to MTC. Other situations, benign or pathological, can explain these variations.

Causes of High Calcitonin

The most significant elevation is observed in medullary thyroid carcinoma. Associated symptoms may include a neck lump, difficulty swallowing, or more rarely, diarrhea and hot flashes. Faced with a high level, the doctor may request tests such as a thyroid ultrasound or a calcium stimulation test to confirm the diagnosis.

Other conditions can also cause a moderate increase in calcitonin:

• Chronic kidney failure.
• Certain other tumors (neuroendocrine).
• Pregnancy or breastfeeding.
• Taking certain medications (especially proton pump inhibitors, used for stomach acidity).

Causes of Low Calcitonin

A very low, even undetectable, calcitonin level is much more common and generally less concerning. It is most often observed in people who have undergone a total thyroidectomy (removal of the thyroid). In this case, the absence of C cells logically explains the absence of hormone production.

Some researchers are studying a potential link between persistently low calcitonin levels and an increased risk of bone fragility (osteoporosis), particularly in postmenopausal women. However, this marker is not routinely used for the diagnosis of osteoporosis.

What to Do Based on Your Results?

The course of action depends on the calcitonin level and the clinical context. Your doctor is the only one who can advise you on the appropriate steps.

When to Consult a Specialist?

A prompt consultation with an endocrinologist is recommended if:

• Your calcitonin level is significantly elevated.
• You have a palpable lump in your neck.
• You have a family history of medullary thyroid carcinoma.
• Your level increases over several successive tests.

Simple monitoring may be sufficient if the elevation is very slight, stable, and no alarming cause is identified after an initial assessment.

Tips on Lifestyle and Diet

Although there is no natural method to normalize a pathological calcitonin level, a healthy lifestyle supports overall bone and metabolic health. This includes a balanced diet rich in calcium and vitamin D, regular physical activity, and quitting smoking. These measures are beneficial for everyone, regardless of calcitonin levels.

Frequently Asked Questions about Calcitonin

Does the calcitonin test require fasting?

Generally, fasting is not strictly mandatory for this test. However, some laboratories recommend it to standardize conditions. A meal very rich in calcium just before blood draw could theoretically slightly influence it. Follow your doctor’s or the laboratory’s instructions.

Why is my calcitonin low despite a calcium-rich diet?

Calcium regulation is complex and involves several hormones, including parathyroid hormone (PTH). A high calcium intake alone does not guarantee a high calcitonin level. Furthermore, after thyroid removal, the level will be low regardless of diet.

Is there a link between low calcitonin and fracture risk?

Some studies suggest an association between low calcitonin levels and an increased risk of fracture, particularly after menopause. Calcitonin helps preserve bone mass. Its prolonged absence could therefore contribute to weakening it. This area of research is still being explored.

Can certain medications alter my calcitonin level?

Yes. Proton pump inhibitors (PPIs), used for stomach issues, are known to be able to cause a moderate elevation of calcitonin. It is therefore crucial to inform your doctor of all medications you are taking before interpreting the results.

What is the role of calcitonin in the presence of a thyroid nodule?

Its measurement is a very effective tool. Faced with a thyroid nodule, a very high calcitonin level almost certainly indicates a diagnosis of medullary cancer. This is why this test is often performed as part of a nodule workup.

Is calcitonin a good monitoring marker after surgery for MTC?

Absolutely. After complete surgery for medullary cancer, the calcitonin level should become undetectable. A re-increase in this level over time is the first sign of disease recurrence, often well before it is visible on imaging.

Additional resources

• To deepen your knowledge of this blood marker, click here.
• To extend your knowledge and decipher other markers, more articles are available here.

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