Thyroid Tests

Thyroid tests (or thyroid function tests) check to see if your thyroid gland works as it should. There are different types of thyroid tests, but they all fall under two categories:

• Blood tests: These tests measure certain hormones and antibodies in your blood.
• Imaging and nuclear medicine imaging: These tests show the size and shape of your thyroid. Nuclear medicine imaging tests can also show how well your thyroid works.

Why is it done?

You might need a thyroid test if you have symptoms like fatigue, restlessness, irritability or unexplained weight changes. Thyroid tests can help diagnose thyroid diseases like:

• Hypothyroidism
• Hyperthyroidism
• Thyroiditis
• Graves’ disease
• Hashimoto’s disease
• Thyroid cancer

What test your provider recommends depends on your symptoms and what they want to learn from the test. Ask your healthcare provider what each one does and what it means if you’re not sure.

How do thyroid tests work?

The tests work differently based on if it’s a blood test or an imaging/nuclear medicine test.

Thyroid blood tests

Blood tests measure certain hormones and antibodies in your blood. Too many or too few of these hormones or antibodies might mean that you have thyroid disease. During a thyroid blood test, a provider will take a sample of your blood and send it to a lab for analysis.

Most of the time, you don’t need to do anything special to prepare. Your healthcare provider will let you know if you need to stop eating or drinking before your test.

The most common thyroid blood tests are:

• TSH (thyroid-stimulating hormone): This is usually the first test most providers recommend. TSH tells your thyroid gland to make thyroid hormones (T3 and T4).
• T3 (or free T3): Triiodothyronine (T3) is one of two main hormones your thyroid makes.
• T4 (or free T4): Thyroxine (T4) is the other main type of hormone your thyroid makes.
• Thyroid antibody panel: These tests tell your provider if there are thyroid antibodies in your blood. Having thyroid antibodies might mean you have an autoimmune disorder.
• Calcitonin: This test detects high calcitonin levels, which can be a sign of a certain type of thyroid cancer. It’s not part of a routine thyroid test and most people don’t need it.
• Thyroglobulin: Thyroglobulin tests may be used after thyroid cancer treatment to see if thyroid cancer has returned. It’s not part of a typical thyroid test.

Thyroid imaging/nuclear medicine scans

Thyroid imaging tests can give your provider more information about the size, shape and function of your thyroid. Providers might recommend imaging tests after you’ve already had thyroid blood tests. They may also order tests that use contrast material to get more detailed pictures.

Some examples of imaging or nuclear imaging scans are:

• Thyroid ultrasound: Providers use ultrasound to detect lumps (nodules) in your neck.
• Thyroid CT or MRI scan: In most cases, your provider will use contrast material with these tests to highlight areas of concern. Contrast materials help get detailed pictures.
• Radioactive iodine uptake test: This test uses small amounts of radioactive materials and a special camera to show your thyroid’s size, shape and function. It can provide more information than other imaging tests (like an ultrasound).

How to prepare for thyroid imaging tests

If your healthcare provider plans to use a contrast material, you might need to stop eating or drinking for a few hours before your procedure.

Your provider will tell you if you need to make any special preparations. Always be sure to tell your provider your full medical history, including what medications you take, if you have allergies, or if you’re pregnant or breastfeeding.

What are the risks of thyroid tests?

There’s little to no risk of a thyroid blood test. You may have side effects, like bruising in your arm from giving a blood sample.

The risks for imaging and nuclear medicine scans could include:

• Allergic reaction to contrast material, like itching or rash
• Exposure to low doses of radiation

What can I expect after a thyroid test?

Your healthcare provider should get your results within a few days. Once they review the results, they’ll call you to discuss them or schedule a follow-up visit.

If your blood test levels are outside of the normal range, they may recommend monitoring, more testing or treatment.

If your scans show a lump on your thyroid, your provider may recommend a needle biopsy, also called an FNA (fine needle aspiration). This will tell them whether the lump is noncancerous or cancerous.

What do my thyroid test results mean?

Thyroid test results tell your provider how well your thyroid is working. Blood tests show if your thyroid hormone levels are typical for your age and sex. Imaging tests give slightly different information and focus more on the appearance and function of your thyroid.