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What Does A Blood Test Show For Thyroid

How Should I Prepare For A Thyroid Function Test

TSH test explained | Thyroid stimulating hormone test | Thyroid function test | Blood TSH test

For the most part, you do not need to do anything before having this test. However, some medicines may change the result of the thyroid function test.

  • Tell your doctor about all prescription and non-prescription medication you take.
  • If you are taking thyroid medicines, tell your doctor when you took your last dose. Your doctor may ask that you stop taking thyroid medicines temporarily before having this test.

Thyroid #4 Comprehensive Blood Test Panel Includes:

Thyroid Panel with Thyroid-Stimulating Hormone : Thyroid function is critical to your metabolism and affects your energy level, heart rate, weight control, and more. The thyroid-stimulating hormone is produced in the pituitary gland and stimulates the production of thyroid hormones. The TSH helps identify an underactive or overactive thyroid state. This comprehensive evaluation of your thyroid hormone levels includes T-3 Uptake, T4, Free Thyroxine Index , and Thyroid-Stimulating Hormone .

Free T3: Free T3 is for evaluating thyroid function and assessing abnormal binding protein disorders.

Free T4: Free T4 may be indicated when binding globulin problems are perceived, or when conventional test results appear to be inconsistent with clinical observations. It is normal in those with high thyroxine-binding globulin hormone binding who are euthyroid . It should also be normal in familial dysalbuminemic hyperthyroxinemia.

Thyroid Peroxidase Antibodies: Antibodies to thyroid microsomes are present in 70% to 90% of patients with chronic thyroiditis. They are also present in smaller percentages of patients of other thyroid diseases. Antibody production may be confined to lymphocytes within the thyroid, and serum may be negative. Small numbers of people with no evidence of disease may have antibodies. This is more frequent in females and increases with age.

Thyroid-stimulating Immunoglobulin : TSI is a second-order testing for autoimmune thyroid disease, including:

How Are Thyroid Tests Done

In order to properly test the hormone levels of your thyroid, a blood draw will be performed by your doctor or at a lab.

Prior to the blood draw, you will be asked to sit in a chair, roll up your sleeves and relax while a nurse or technician prepares your arm for the draw.

A band of rubber will be tightly tied around your upper arm to force the veins to swell. This makes it easier for a vein to be found so the needle can be inserted.

Having blood drawn is mostly painless, although it is possible to feel a sharp prick when the needle is inserted. This is typically a very quick sensation.

Once the blood has been fully drawn, the needle will be removed and a small bandage will be placed over your wound.

Before your tests are performed, you should tell your doctor if youre taking any medication or if you may be pregnant. This may alter the results of your test.

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Understanding Thyroid Stimulating Hormone

As mentioned above, the thyroid stimulating hormone is produced by the pituitary gland. It works sort of like the master of the hormones, and rules the production of T3 and T4 from its control center.If you have too much TSH, it might mean that your thyroid gland isnt making enough T3 or T4. Remember, the TSH is supposed to stimulate the thyroid gland but if the gland isnt responding, then youll have too much TSH in your system.If your TSH levels are too low, it may mean that your thyroid gland is making too much thyroid hormone. This excessive thyroid production could actually suppress the TSH.

A word of warning for pregnant women: Its incredibly important that your hormones are balanced in pregnancy, as thyroid stimulating hormone plays a role in the development of a healthy fetus.

Thyroid Testing: How It Works

What Does A Thyroid Test Show

Thyroid tests use a blood sample to measure various hormone levels. Thyroid-stimulating hormone , for example, is often measured to indirectly check if your thyroid gland is producing enough thyroid hormones. TSH levels are usually higher than normal if you have an underactive thyroid .

Thyroid function tests can also measure thyroid hormones like thyroxine to provide a better understanding of how low â or how high â your thyroid hormone levels are.

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What More Should I Know About Thyroid Blood Tests

Ranges noted here are approximate your providers may differ slightly. Its important that you remember abnormal readings do not necessarily mean a thyroid disorder is present, as each test can be affected by a variety of factors.

No preparation is required for these tests. They can be taken any time of day without fasting.

Last reviewed by a Cleveland Clinic medical professional on 12/27/2019.


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1. Carvalho GA, et al. The clinical use of thyroid function tests, 2013

2. Wartofsky L, et al. The evidence for a narrower thyrotropin reference range is compelling, 2005

3. Hollowell JG, et al. Serum TSH, T, and thyroid antibodies in the United States population : National Health and Nutrition Examination Survey , 2002

4. Dunn JT. Guarding our nations thyroid health, 2002

5. Surks MI, et al. Age-specific distribution of serum thyrotropin and antithyroid antibodies in the US population: implications for the prevalence of subclinical hypothyroidism, 2007

6. Fontes R, et al. Reference interval of thyroid stimulating hormone and free thyroxine in a reference population over 60 years old and in very old subjects : comparison to young subjects, 2013

7. Kumar A, et al. Thyroid function tests in pregnancy, 2013

8. Hubner U, et al. Continuous age-dependent reference ranges for thyroid hormones in neonates, infants, children and adolescents established using the ADVIA Centaur Analyzer, 2002

9. Lewandowsky K. Reference ranges for TSH and thyroid hormones, 2015

10. Vadiveloo T, et al. Age- and gender-specific TSH reference intervals in people with no obvious thyroid disease in Tayside, Scotland: the Thyroid Epidemiology, Audit, and Research Study , 2013

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What Is Thyroid Function Test

Thyroid function test is used to check how well your thyroid is working and to find the cause of problems such as hyperthyroidism or hypothyroidism. The thyroid is a small, butterfly-shaped gland in the front of your neck that makes two thyroid hormones: thyroxine and triiodothyronine . Thyroid hormones control how your body uses energy, so they affect nearly every organ in your body, even your heart.

Thyroxine and triiodothyronine circulate almost entirely bound to specific transport proteins, and there are some situations which these proteins could change their level in the blood, producing also changes in the thyroxine and triiodothyronine levels .

The thyroid function test usually includes:

The total T4 and total T3 tests have been used for many years, but they can be affected by the amount of protein available in the blood to bind to the hormone. The free T4 and free T3 tests are not affected by protein levels and are thought by many to be more accurate reflections of thyroid hormone function. In most cases, the free T4 test has replaced that of the total T4 test. However, some professional guidelines recommend the total T3 test, so either total T3 or free T3 test may be used to assess thyroid function.

Thyroid blood tests help health care professionals diagnose thyroid diseases such as:

Your doctor will start with blood tests and may also order imaging tests.

  • Increases, decreases, and changes in the proteins that bind T4 and T3
  • Pregnancy

What is reverse T3?

T3 Resin Uptake Results


A T3 resin uptake, also known as a T3RU, is a blood test that measures the binding capacity of a hormone called thyroxin-binding globulin . If your T3 level is elevated, your TBG binding capacity should be low.

Abnormally low levels of TBG often indicate a problem with the kidneys or with the body not getting enough protein. Abnormally high levels of TBG suggest high levels of estrogen in the body. High estrogen levels may be caused by pregnancy, eating estrogen-rich foods, obesity, or hormone replacement therapy.

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Heres What You Need To Know About The Reverse T3 Blood Test

Most of the time, the reverse T3 blood test will not be ordered for those patients who have been hospitalized for some reason. An acute illness will also affect hormone levels in such a way that it may seem like someone is suffering from secondary hypothyroidism. Unless there is a severe issue which needs to be addressed, this blood test will only be ordered in an outpatient situation.

There are other health issues that may also change how the body creates T3. This includes taking or being exposed to estrogen, suffering from liver disease, and have a resistance to hormones. Certain birth control pills or a large dose of aspirin can affect these blood test results. Anyone taking these items will want to discuss their impact with their medical provider if the reverse T3 blood test is being considered.

The reverse T3 test is a way to determine, therefore, how sick a person may be from a systemic or acute illness because this hormone stops the tissues from absorbing the hormone to consume energy. It is believed that high reverse T3 levels help the body be able to conserve total energy until the stress upon it has been relieved. If high levels of this hormone are in place consistently even when feeling well, then this can be symptomatic of a condition called Non-Thyrodial Illness.

In People Without Known Thyroid Disease

A high TSH in people who are not undergoing thyroid disease treatment usually indicates the presence of primary hypothyroidism.

This is by far the most common form of hypothyroidism, and it occurs because the thyroid gland produces an inadequate amount of thyroid hormones. The pituitary gland senses these low levels and increases the production of TSH.

An elevated TSH may also occur with normal thyroid function due to the presence of antibodies, proteins made by the immune system.

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What Imaging Tests Do Doctors Use To Diagnose And Find The Cause Of Thyroid Disease

Your health care professional may order one or more imaging tests to diagnose and find the cause of thyroid disease. A trained technician usually does these tests in your doctors office, outpatient center, or hospital. A radiologist, a doctor who specializes in medical imaging, reviews the images and sends a report for your health care professional to discuss with you.

Questions To Ask Your Endocrinologist:

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  • What tests do I need to check my thyroid levels?
  • What are the normal ranges for each hormone?
  • Are my T3, T4, and TSH levels normal?
  • Are my symptoms indicative of a thyroid disorder?
  • How can we correct any issues with the levels through medication or lifestyle changes?
  • Are there any side effects to the medications?
  • How long does it take before the medicine starts to work?

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Understanding The Reverse T3 Blood Test Results

The reverse T3 blood test, which is also referred to as the reverse triiodothyronine test, is ordered by a medical professional when there is a need to evaluate thyroid gland function. It may be used in order to diagnose thyroid disease, often hyperthyroidism, and to determine the cause of the order. Those with a thyroid diagnosis may also have this test ordered regularly to monitor the effectiveness of their treatment plan.

Women who are pregnant may also have this test ordered by their provider to monitor thyroid levels. A pregnancy can cause a total increase of free and total T3 levels, even though thyroid disease may return to normal after birth.

Is There Anything Else I Should Know

In the past, panels of tests were more common. More recently, however, the practice has been to order, where possible, one initial or screening test and then follow up with additional testing, if needed, to reduce the number of unnecessary tests. With thyroid testing, one strategy is to screen with a TSH test and then order additional tests if the results are abnormal or if clinical suspicions warrant.

Your thyroid hormone test results can be affected by:

  • Increases, decreases, and changes in the proteins that bind T4 and T3
  • Pregnancy

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What Do The Reverse T3 Blood Test Results Mean

There will be three total blood test results that will be considered when evaluating what may be causing a patients bothersome signs and symptoms. Here are what the typical test results would be and what their potential meaning would represent.

  • TSH / T4 / T3 : Mild hypothyroidism.
  • TSH / T4 / T3 : Hypothyroidism.
  • TSH / T4 / T3 : Mild hyperthyroidism.
  • TSH / T4 / T3 : Hyperthyroidism.
  • TSH / T4 / T3 : Secondary hypothyroidism.
  • TSH / T4 / T3 : Thyroid hormone resistance syndrome.

The reason why the reverse T3 blood test is ordered on a regular basis once a health issue has been discovered is that the medication may cause additional symptoms by changing hormone levels. If an anti-thyroid medication stabilizes T3 levels, then the symptoms may fade and the treatment considered to be effective. If T3 levels are elevated, then new symptoms may wind up occurring.

How Much Does The Test Cost

Low Thyroid Symptoms Despite Blood Tests?

The cost of a thyroid panel depends on your insurance coverage and where the test is performed. If ordered by a doctor, insurance normally covers a thyroid panel except for any patient cost-sharing such as copays or deductibles. Check with your health plan and health care provider for specific cost details.

At-home thyroid tests usually cost less than $150, which includes the cost of shipping your blood sample to the lab.

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Where To Get A Thyroid Function Test

NHS thyroid function test The NHS offer blood tests which can be done at your GPs or a local hospital. A trained nurse or doctor will take your blood, usually a venous sample.

Home thyroid function test Its possible to order a home thyroid function test kit online and do it yourself. For this test, youll use a lancet to collect a finger-prick blood sample. Your results will be reviewed by a GP and are available for you to view online.

What Can A Thyroid Test Detect

  • What Can a Thyroid Test Detect?

When most people hear about the thyroid, they associate it with the inability to lose or gain weight, but it is responsible for much more than that.

In fact, hormones made by the thyroid can impact how quickly your heart beats, how deep you breathe, your body temperature, womens menstrual cycles and cholesterol levels.

Unfortunately, more than 12 percent of people will deal with a thyroid problem in their life, with women being more likely to deal with this issue than men.

Heres what you need to know about the thyroid and what a test can detect.

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What Are Thyroid Function Tests Used For

Thyroid function tests are usually done to find out whether the thyroid gland is working properly. This is mainly to diagnose an underactive thyroid gland and an overactive thyroid gland .

People with some conditions have an increased risk of thyroid problems and so are often advised to have thyroid function tests undertaken each year. This conditions include:

Certain medicines can also affect the function of your thyroid – for example, amiodarone and lithium.

Thyroid function tests can also be done to:

  • Monitor treatment with thyroid replacement medicine for people who have hypothyroidism.
  • Check thyroid gland function in people who are being treated for hyperthyroidism.
  • Screen newborn babies for inherited problems with the thyroid gland.

How Does A Blood Test For Hypothyroidism Work

What does the blood test actually tell about your thyroid ...

How to test for hypothyroidism?

Itâs important to note that there is no hypothyroidism test that can check thyroid hormones andâbased only on those test resultsâconclusively determine if someone has hypothyroidism. Thatâs because both thyroid hormone testing and a physicianâs evaluation of symptoms and medical history is required for a diagnosis.

A blood test for hypothyroidism is based on your levels of thyroid-stimulating hormone and the thyroid hormones T3 and T4. Because TSH signals the thyroid gland to produce more thyroid hormones, unusually high levels of TSH can mean that your thyroid isnât making enough hormones.

A thyroid lab test might also measure T3 and T4 to reveal just how low your thyroid hormone levels are, which can help your healthcare provider decide on a treatment strategy.

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Is There Anything Else I Need To Know About A Thyroxine Test

Thyroid changes can happen during pregnancy. Although it is not common, some women can develop thyroid disease during pregnancy. Hyperthyroidism happens in about 0.1% to 0.4% of pregnancies, while hypothyroidism happens in approximately 2.5% of pregnancies.

Hyperthyroidism, and less often, hypothyroidism, may remain after pregnancy. If you develop a thyroid condition during pregnancy, your health care provider will monitor your condition after your baby is born. Also, if you have a history of thyroid disease, be sure to talk with your health care provider if you are pregnant or are thinking of becoming pregnant.

What You Can Do

If you have definite symptoms of hypothyroidism, you should talk to your clinician about being tested. If your LDL cholesterol has been advancing or your weight has been creeping up unexplainably, you’ll want to discuss getting a test. If you’re 60 or older and generally healthy, it’s still a good idea to check with your doctor to see whether your medical history suggests you might benefit from testing.

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Who Orders My Blood Tests

Your doctor typically orders blood tests for you during a physical, checkup, or an appointment intended to screen for a specific condition.

Its possible to order your own blood tests without a doctor through laboratories like LabCorp and Quest Diagnostics, but health insurance may not cover these tests.

While such blood tests may more accessible and convenient, it may be harder to interpret the results without a medical professional.

Some blood testing facilities may also not give you accurate results.

One infamous case of this is Theranos. The California biotechnology firm shut down in 2018 when an investigation uncovered lies and fraud around the accuracy of its private blood-testing technology.

Currently, litigation is underway against the founder and chief executive of the company, Elizabeth Holmes.


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