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Diagnostic Tests 2023

6 tests that evaluate the thyroid (and when to do it)

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6 tests that evaluate the thyroid (and when to do it)
6 tests that evaluate the thyroid (and when to do it)
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To identify diseases that affect the thyroid, the doctor may request several tests to evaluate the size of the glands, the presence of tumors and thyroid functioning. Thus, the doctor can recommend the dosage of hormones that are directly linked to the functioning of the thyroid, such as TSH, free T4 and T3, as well as imaging tests to check for the presence of nodules, such as thyroid ultrasound, for example.

However, more specific tests such as scintigraphy, biopsy or antibody dosage may also be requested, which may be recommended by the endocrinologist during the investigation of certain diseases, such as thyroiditis or thyroid tumors, for example. Look for signs that could indicate thyroid problems.

Blood test
Blood test

Blood test

The most requested tests to evaluate the thyroid are:

1. Thyroid hormone measurement

The dosage of thyroid hormones through a blood test allows the doctor to evaluate the functioning of the gland, making it possible to verify if the person has alterations suggestive of hypo or hyperthyroidism, for example.

Although reference values may vary depending on the person's age, presence of pregnancy and laboratory, generally normal values include:

Thyroid Hormone Reference Value
TSH 0, 3 and 4.0 mU/L
T3 Total 80 to 180 ng/dl
T3 Free 2, 5 to 4 pg/ml

T4 Total

4.5 to 12.6 mg/dl
T4 Free 0.9 to 1.8 ng/dl

After identifying the change in thyroid function, the doctor will assess the need to request other tests that help identify the cause of these changes, such as ultrasound or antibody dosage, for example.

Understand possible TSH exam results

2. Antibody dosage

The blood test can also be done to measure antibodies against the thyroid, which can be produced by the body in some autoimmune diseases, such as Hashimoto's thyroiditis or Graves' disease, for example. The main ones are:

  • Anti-peroxidase (anti-TPO) antibody: present in the vast majority of cases of Hashimoto's thyroiditis, a disease that causes cell damage and gradual loss of thyroid function;
  • Anti-thyroglobulin (anti-Tg) antibody: is present in many cases of Hashimoto's thyroiditis, however, it is also found in people without any thyroid disorder, so, its detection does not always indicate that the disease will develop;
  • Anti-TSH receptor antibody (anti-TRAB): may be present in cases of hyperthyroidism, mainly caused by Graves' disease. Learn what it is and how to treat Graves' disease.

Thyroid autoantibodies should only be ordered by physicians in cases where thyroid hormones are altered, or when thyroid disease is suspected, as a way of helping to clarify the cause.

3. Thyroid ultrasound

The thyroid ultrasound is done to evaluate the size of the gland and the presence of changes such as cysts, tumors, goiter or nodules. Although this test cannot tell if a lesion is cancerous, it is very useful to detect its characteristics and to guide the puncture of nodules or cysts to aid in the diagnosis.

thyroid ultrasound

4. Thyroid scintigraphy

A thyroid scan is a test that uses a small amount of radioactive iodine and a special camera to take an image of the thyroid and identify the level of activity in a nodule.

It is mainly indicated to investigate suspicious nodules of cancer or whenever hyperthyroidism is suspected caused by a hormone-secreting nodule, also called a hot or hyperfunctioning nodule. Learn how thyroid scintigraphy is done and how to prepare for the exam.

5. Thyroid biopsy

A biopsy or puncture is done to identify whether the thyroid nodule or cyst is benign or malignant. During the examination, the doctor introduces a fine needle towards the nodule and removes a small amount of the tissue or fluid that forms this nodule, so that this sample can be evaluated in the laboratory.

A thyroid biopsy can be painful or uncomfortable because this test is not done under anesthesia and the doctor may move the needle during the test to be able to take samples from various parts of the nodule or to aspirate more fluid. The exam is quick and lasts about 10 minutes, after which the person must remain with a bandage in place for a few hours.

6. Thyroid self-exam

The thyroid self-examination can be done to identify the presence of cysts or nodules in the gland, being important to help detect any changes early and prevent disease complications and should be done, mainly, by women with more age 35 or with a family history of thyroid problems.

To do it, follow these steps:

  • Hold a mirror and identify the place where the thyroid is located, which is just below the Adam's apple, known as "gog√≥";
  • Tilt your neck back a little to better expose the region;
  • Drink a sip of water;
  • Observe the movement of the thyroid and identify if there is any bulge, asymmetry.

If any thyroid alteration is noticed, it is important to seek the care of the endocrinologist or general practitioner so that the investigation is carried out with tests that may or may not confirm a thyroid alteration.

When you need to have thyroid tests

Thyroid exams are recommended for people over the age of 35 or younger if there are symptoms or a family history of thyroid changes, women who are pregnant or wishing to become pregnant, and for people who have noticed changes during a thyroid self-exam or medical examination.

In addition, tests are also indicated after radiation treatment for neck or head cancer and during treatment with drugs such as Lithium, Amiodarone or Cytokines, for example, which can interfere with thyroid function.

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