Calcitonin: what it is, what it tells you and when it’s tested

Calcitonin is a hormone made by a few cells in your thyroid, the C cells. In adults it matters little for the body. In medicine it is used mainly as a marker for a rare thyroid cancer, medullary carcinoma. A high calcitonin, though, does not mean cancer in most cases.

When it’s tested

Doctors or endocrinologists mostly order it in three cases: in some people with a thyroid nodule, when medullary carcinoma runs in the family, and in check-ups for people already treated for this cancer, together with CEA.

For nodules, experts disagree: some order it for everyone, others only in selected cases. The specialist decides.

It is not a test to look for cancer in people who feel well: medullary cancer is rare, and a slightly high calcitonin almost always has other causes. That is why Rosa does not test it. Rosa measures TSH, the first test for the thyroid, and calcium.

What it tells you, and what it does not

A normal calcitonin makes medullary cancer very unlikely, but does not completely rule it out.

A high calcitonin does not mean cancer. Among people with a nodule and calcitonin above 10 pg/mL, fewer than one in ten actually has medullary carcinoma. In the others there is another cause: kidneys, medicines, smoking, thyroiditis.

That is why a high value is repeated and read with a specialist, together with an ultrasound and, if needed, other tests.

That is why it is read together with other tests:

Normal calcitonin levels

The lab decides what is normal, and it is usually different for women and men. Men have higher calcitonin.

In a large group of healthy people, 95 women in a hundred had calcitonin below 5.2 pg/mL, and 95 men in a hundred below 11.7. Your report may print slightly different limits: those are the ones that count.

Some reports write the unit as ng/L: it is the same thing, and the numbers do not change. Once the thyroid has been removed, calcitonin is usually no longer measurable.

If your calcitonin is high or low

What causes high calcitonin

There is often more than one. The most common are not cancer:

If you have had medullary carcinoma, or it runs in your family

After surgery, calcitonin and CEA are the two tests your specialist uses to check that all stays quiet. How they change over time, at the same lab, counts more than a single value.

Some medullary carcinomas are inherited. If there have been cases in your family, your doctor may offer you a genetic test. If it is positive, you plan the check-ups and choices with a specialist.

What can skew the result

A few things raise it without any cancer. It helps to know them before your blood test.

When to worry

Talk to your doctor if:

Frequently asked questions

What are normal calcitonin levels? They differ for women and men. In healthy people, 95 women in a hundred are below 5.2 pg/mL and 95 men in a hundred below 11.7. The range on your own report is what counts.

High calcitonin: is it cancer? Almost always no. Kidneys, stomach medicines, smoking, high calcium and thyroiditis raise it far more often. Even among people with a nodule and calcitonin above 10 pg/mL, fewer than one in ten has medullary carcinoma.

High calcitonin: when should I worry? When it is high and there is a thyroid nodule, when it rises over time, or when medullary carcinoma runs in your family. Then an endocrinologist reads it, usually with an ultrasound.

Is calcitonin a prevention test? No. In people who feel well and have no nodules, the cancer it looks for is very rare, and a high value would almost always have other causes. It is only measured when there is a reason.

Does Rosa test calcitonin? No. Rosa measures TSH, calcium and eGFR, which shows how well your kidneys filter. If your doctor wants calcitonin, they order it separately.

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