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Thyroid Panel: Thyroid Function Test
Updated on November 4, 2022
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Thyroid Panel: Thyroid Function Test

The thyroid panel or thyroid function test is a series of lab tests that evaluates your thyroid function. 

“The test measures the hormone called TSH or Thyroid-stimulating hormone, which is produced by a gland in the brain. It also measures T3 and T4 which are produced by the thyroid glands,” says our medical expert Dr. Rizza Mira. 

It can help with the diagnosis and treatment of thyroid disorders.

Quick Facts On Thyroid Test Panel

  • Uses one blood sample for a group of blood tests
  • It can tell a lot about how well your thyroid gland is working
Thyroid Panel: Thyroid Function Test 3

Why Take A Thyroid Panel Test?

The thyroid produces hormones that regulate many bodily functions, like metabolism. You may experience a range of symptoms when it isn't working enough or is overactive.

Your healthcare provider can use a thyroid panel to assess how your thyroid is functioning. It measures the hormone levels in your blood to detect thyroid dysfunction.

Doctors can also use thyroid function tests to monitor the treatment of an overactive thyroid or hyperthyroidism. 

These tests are also used before radioactive iodine therapy or surgery. They can also determine how the person is doing with levothyroxine therapy. 

Levothyroxine medication replaces the missing or lacking hormones caused by:1

  • Hypothyroidism
  • Thyroid cancer
  • Thyroid nodules
  • Autoimmune destruction of thyroid gland
  • Goiters

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What Does A Thyroid Panel Check For?

The thyroid panel measures several hormones, including:

  • Thyroid-stimulating hormone (TSH)
  • Free thyroxine (T4)
  • Free triiodothyronine or total triiodothyronine (T3)

TSH regulates the production of T4 by the thyroid gland.2 The amount of TSH released by the pituitary gland into the bloodstream also depends on your T3 and T4 levels.

If T3 and T4 levels are low, the pituitary gland signals the thyroid gland to produce more TSH, increasing your hormone levels.3 But when these are above normal, the gland inhibits TSH production. 

When To Take A Thyroid Test

Your doctor may order thyroid testing if your symptoms indicate a thyroid problem. Your signs may depend on whether you have an underactive or overactive thyroid.

The thyroid makes two main hormones — triiodothyronine (T3) and thyroxine (T4). When your thyroid hormones are imbalanced, you may experience symptoms such as:

  • Problems with concentration and memory
  • Unexplained weight gain or weight loss
  • Lack of or excessive energy 
  • Depression, anxiety, and other mood-related issues
  • Dry skin and hair
  • Hair loss
  • Sensitivity to cold or heat 
  • Changes in your menstrual cycle

How Much Does A Thyroid Test Cost?

The cost depends on whether or not you have insurance and how you’ll take the test. 

Insurance usually covers thyroid panels ordered by a doctor. However, they may exclude any additional cost, such as co-pays or deductibles.

You should check with your insurance provider and doctor for the actual cost.

How Thyroid Testing Works

A thyroid panel test provides several measurements with a single blood sample. If your doctor is conducting the lab work, they will use a needle to draw blood from a vein in your arm.

Before Your Thyroid Test

You don’t have to prepare for a thyroid test. However, you must inform your doctor about any prescription or over-the-counter medications you’re taking. 

Also, if you’re on hormone treatment for thyroid disease, you should have your blood sample taken before your first dose for the day.

Tell your doctor if you're feeling unwell. They will likely reschedule testing because some illnesses can influence your test results.

Taking these steps ensures the accuracy of your test results.

During Your Test

If your blood sample is taken at the doctor's office or a lab, they will collect your blood using a needle inserted through your arm’s vein.

The lab technician will wrap a tourniquet around your upper arm. Next, they will disinfect the area where the needle goes in.

You might feel a quick sting from the needle but the pain is usually bearable and doesn't last long. The blood draw takes less than a minute most of the time.

After Your Test

As soon as they collect your blood, the medical technician will put a band-aid or cotton swab on the injection site to stop the bleeding. They'll instruct you to leave it on for at least an hour.

You can resume your normal activities after the test. However, your doctor may advise you to hold off from strenuous tasks, especially ones that may strain your arm. 

Call your doctor if the injection site has pain or bleeding that doesn't go away or if there are signs of infection.

Understanding Your Thyroid Test Results

Your test results contain the lab’s findings for each thyroid hormone. It may include reference ranges for normal outcomes, and indicate whether your results are within this range or not.

The reference range for each hormone depends on your age, current health condition, and the lab that conducts the blood work. Your doctors will simultaneously analyze your results. 

For the American Board of Internal Medicine, these are the normal ranges of a thyroid panel:4

  • TSH Levels — 0.5 to 4 mIU/L
  • Free T4 Levels — 0.8 and 1.8 ng/dL in adults
  • Total T3 Levels — 80 to 180 ng/dL

Changes in TSH levels may be an early warning sign of a thyroid disorder.5 It usually occurs before the thyroid hormone levels get too high or too low. 

“Deranged TSH levels are interpreted together with T3 and T4 values. However, when only the TSH value is abnormal, this may be a sign of early thyroid disease. This condition is called subclinical disease,” says Dr. Rizza Mira. 

However, free T4 and total T3 values may also suggest the extent of a thyroid problem.

Can You Take A Thyroid Test At Home?

Yes. You can have a thyroid function test from the comfort of your home. Most at-home thyroid test kits have easy-to-follow instructions and collection tools.

You need to collect a finger-prick blood sample and send it back to the company for analysis. They’ll send your results after running the thyroid panel on your sample.

Most at-home thyroid tests are affordable. They usually cost less than $150, which covers the cost of sending your blood sample back to the lab.

Even though you can test your thyroid levels at home, it shouldn’t replace a visit to your doctor. Not only do doctors interpret the results of your lab exam, they also correlate them with clinical findings.

At-home thyroid testing may not be as accurate as tests done in a lab, so a doctor is your best bet. 

If your at-home test shows thyroid levels that aren’t normal, you can take your results to a doctor. They might suggest a thyroid panel to assess your condition.

Thyroid Panel: Thyroid Function Test 4

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Resources

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  1. Levothyroxine.” NHS UK. 
  2. The thyroid gland.” Department of Health Western Australia.
  3. How Your Thyroid Works.” Endocrine Web.
  4. ABIM Laboratory Test Reference Ranges ̶ January 2022.” American Board of Internal Medicine.
  5. Thyroid Function Tests.” American Thyroid Association.
Dr. Rizza Mira
Dr. Rizza Mira
Medical Reviewer
Dr. Rizza Mira is a medical doctor and a general practitioner who specializes in pediatrics, nutrition, dietetics, and public health.

As a pediatrician, she is dedicated to the general health and well-being of children and expecting parents. She believes that good nutrition, a healthy lifestyle, and prevention of illness are key to ensuring the health of children and their families.

When she’s not in the hospital, Rizza advocates and mobilizes causes like breastfeeding, vaccination drives, and initiatives to prevent illness in the community.
Cristine Santander
Cristine Santander
Content Contributor
Cristine Santander is a content writer for KnowYourDNA. She has a B.S. in Psychology and enjoys writing about health and wellness.
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