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Diagnostic Tests 2023

Thyroglobulin: because it can be high or low

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Thyroglobulin: because it can be high or low
Thyroglobulin: because it can be high or low

Thyroglobulin is a tumor marker widely used to assess the development of thyroid cancer, especially during its treatment, helping the physician to adapt the treatment method and/or doses, according to the results.

Although not all types of thyroid cancer produce thyroglobulin, the most common types do, so levels of this marker are usually increased in the blood in the presence of cancer. If the thyroglobulin value continues to increase over time, it means that the treatment is not having the desired effect and needs to be changed.

In rarer cases, the thyroglobulin test can still be used to determine the cause of hyperthyroidism or hypothyroidism, for example.


When to take the thyroglobulin test

The thyroglobulin test is usually done before starting any treatment for thyroid cancer, so that there is a baseline value for comparison, and then it is repeated several times over time to assess whether the form of treatment chosen is having resulted in the cure of cancer.

If you have chosen to have surgery to remove the thyroid, this test is also often done after surgery to ensure that there are no cancer cells left in the area, which may be developing again.

In addition, in some cases of suspected hyperthyroidism, the doctor may also order a thyroglobulin test to identify diseases such as thyroiditis or Graves' disease, for example.

See which tests evaluate the thyroid and when to do it.

How to interpret the exam result

The thyroglobulin value in a he althy person, without any thyroid changes, is usually less than 10 ng/mL but can go up to 40 ng/mL. So if the test result is above these values, it may indicate the presence of a thyroid problem.

Although the test result should always be interpreted by the doctor who ordered it, usually the results mean:

High thyroglobulin

  • Thyroid cancer;
  • Hyperthyroidism;
  • Thyroiditis;
  • Benign adenoma.

If you have already had some type of treatment for your cancer, if your thyroglobulin is high it could mean that the treatment had no effect or that the cancer is growing back.

Although thyroglobulin is increased in cancer, this test does not confirm the presence of cancer. In suspected cases, a biopsy is still necessary to confirm the cancer. See the main symptoms of thyroid cancer and how to confirm the diagnosis.

Low thyroglobulin

Since this test is performed on people who already have a thyroid disorder, when the value drops, it means that the cause is being treated and therefore the gland is producing less thyroglobulin.

However, if there was no suspicion of a thyroid problem and the value is very low, it can also indicate a case of hypothyroidism, although it is rarer.

How it is done and how to prepare it

The exam is very simple, it is only necessary to collect a small blood sample from the arm.

In most cases, no preparation is necessary, but depending on the technique used to perform the exam, some laboratories may recommend that you stop taking some vitamin supplements, such as those containing vitamin B7, for at least 12 hours before the exam.

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