Why It Is Done
Thyroid hormone tests are done to:
- Find out what is causing an abnormal thyroid-stimulating hormone test. For more information, see the topic Thyroid-Stimulating Hormone . This is the most common reason for thyroid hormone tests.
- Check how well treatment of thyroid disease is working. The free thyroxine ;value;is;often used to keep track of treatment for hyperthyroidism;or hypothyroidism, if TSH is abnormal or if TSH is normal and a patient has pituitary disease.
What Are Thyroid Peroxidase Antibodies
An antibody is defined as a protective protein produced by the immune system in response to the presence of a foreign substance called an antigen. Antibodies detect and bind to the antigens with a mission to remove them from the body.
In some cases, antibodies attack the bodys own cells, tissues, and organs. This reaction is called autoimmune response. When thyroid antibodies attack healthy cells produced by the butterfly-shaped gland, an autoimmune thyroid disorder can occur.
Thyroid peroxidase functions as a catalyst to the organification and coupling reactions in the production of the T4 hormone. However, thyroid peroxidase antibodies prevent it from doing so. The presence of TPO antibodies indicates that the cause of thyroid disease is an autoimmune disorder such as Hashimotos thyroiditis and Graves disease.
Antibodies that attack thyroid gland induce inflammation and impair the function of this important gland.
Does The Treatment Have Any Side Effects
Because thyroxine medicine is simply replacing a normal chemical produced by the body, giving the correct dose every day should not have any side effects. However, if given too little thyroxine, the child will develop the symptoms of hypothyroidism outlined earlier, and over a long period, may grow more slowly than usual. If the child has too much thyroxine, he or she may develop mild diarrhoea, not put on weight, may be more restless than usual and over a long period may grow more quickly than usual. But, as described above, the correct dose for the child will be calculated on a regular basis, so these effects are unlikely to occur.
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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
What Affects The Test
Reasons the interpretation of your test may be affected:
- Taking certain medicines, such as:
- Corticosteroids, estrogen, progesterone, or birth control pills.
- Antiseizure medicines such as phenytoin or carbamazepine.
- Heart medicines such as amiodarone or propranolol.
- Thyroid Biopsy.
- Other blood tests are often used to check how well the thyroid gland is working.
- Because false-positive results can occur when testing a newborn for congenital hypothyroidism, the thyroid hormone tests may be repeated a few days after initial testing. If the results are still abnormal and congenital hypothyroidism is suspected, additional testing is done.
- Thyroid-stimulating hormone test measures the amount of TSH in the blood and is considered the most reliable way to find a thyroid problem. If the TSH test is abnormal, other thyroid hormone tests such as a FT3 or FT4 may be done. For more information, see the topic Thyroid-Stimulating Hormone.
- Thyroid antibodies test measures the presence of antibodies against thyroid tissue. Antibodies may mean that you have an autoimmune disease such as Hashimoto’s thyroiditis or Graves’ disease.
- Other tests used to investigate problems with the thyroid gland include:
What Is Measured In A Thyroid Test
The main three hormones that are measured in a thyroid blood test are:
TSH is the most sensitive biomarker for thyroid function and is often used to ensure the hormone replacement therapy you are prescribed is working as effectively as it should.
High levels of T3 and T4 often indicate an overactive thyroid, whereas low levels indicate an underactive thyroid.
Thyroid problems can be identified by measuring the level of free T3 in the blood. High levels indicate an overactive thyroid whereas low levels indicate an underactive thyroid.
T3 can be used to:
- test to see if your thyroid is performing properly
- diagnose an overactive thyroid
T3 is only really requested when diagnosing or testing the severity of hyperthyroidism.
Levels of T4 are often used in conjunction with presenting symptoms to identify a thyroid problem, rather than alone.
There are two additional biomarkers that can be added to a thyroid test, these are:
- Thyroglobulin Antibodies
- Thyroid Peroxidase Antibodies
Thyroglobulin is a protein stored in the thyroid gland and aids the production of T3 and T4. Thyroid Peroxidase Antibodies help to identify autoimmune thyroid disease.
Thyroid Disorders And Symptoms
If you dont produce enough thyroid hormones your bodily processes start to slow down. Signs of an underactive thyroid include:
Autoimmune thyroid diseases An autoimmune disease is when your immune system mistakenly attacks your body in this case, thyroid antibodies attack your thyroid. This can lead to a thyroid disorder. Types of autoimmune thyroid diseases include Graves disease or Hashimotos disease .
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When To Take Thyroid Medications To Get Accurate Lab Results
- TSH– This is a pituitary hormone that responds to low/high amounts of circulating thyroid hormone. In advanced cases of Hashimoto’s and primary hypothyroidism, this lab test will be elevated. In the case of Graves’ disease the TSH will be low. People with Hashimoto’s and central hypothyroidism may have a normal reading on this test.;
- Free T3 & Free T4-These tests measure the levels of active thyroid hormone circulating in the body. When these levels are low, but your TSH tests in the normal range, this may lead your physician to suspect a rare type of hypothyroidism, known as central hypothyroidism. ;
How Is The Sample Collected For Testing
A blood sample is taken by a needle placed in a vein in your arm.;A tourniquet is wrapped around your upper arm. It may feel tight. You may feel nothing at all from the needle, or you may feel a quick sting or pinch. The blood sample is collected in a tube, which is sent to the laboratory for analysis.
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What Are Thyroid Replacement Hormones And How Do They Work
Thyroid replacement hormones are medications used to treat hypothyroidism, a condition in which the production of thyroid hormone in the body is abnormally low. Thyroid hormones increase cellular metabolism that is responsible for growth, development of tissues, maintenance of brain function, body temperature regulation and several other cellular processes. Low levels of thyroid hormones in the body can result in many problems given the numerous activities that they mediate. The thyroid gland, a gland found in the lower neck is responsible for the production of thyroid hormones. It produces two main hormones, thyroxine and triiodothyronine . The hormone responsible for most of the biological effects in the body is T3. When T4 is released into the blood by the thyroid gland, most of it is converted to T3 which is responsible for the cellular metabolic processes. Commercially available thyroid hormones are either natural or synthetic . Desiccated thyroid or thyroid extract , a natural thyroid hormone is derived from beef or pork. Levothyroxine sodium , is the synthetic version of thyroxine ,liothyronine sodium , is the synthetic version of tT3 andliotrix is a synthetic thyroid hormone containing a mixture of T4and T3.
Ask Your Doctor About Natural Desiccated Thyroid
In recent years, an increasing number of people are embracing a century-old treatment called natural desiccated thyroid , which is derived from the dried thyroid gland of pigs or cows. NDT delivers T4, T3, and other thyroid hormones in a tablet form and is today used by the likes of Hillary Rodham Clinton and others to manage their hypothyroid symptoms.
While NDT is not officially approved for the treatment of hypothyroidism, it is regulated by the FDA and allowed to be sold by prescription, having been grandfathered in as a standard of care since the 1950s.
NDT is marketed under many different brand names, including Armour Thyroid, Nature-Throid, WP Thyroid, and others.
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Considering Taking A Thyroid Test Look For The Symptoms
Be aware that symptoms of thyroid dysfunction are easy to miss; it is estimated that as many as 1 in 5 people may have sub-optimal thyroid function and do not even know it. So what should you look for? Here are some of the common thyroid symptoms I see in my patients.
Feeling Tired, Sluggish or Low Energy
Everyone goes through times of stress or busy periods that can disrupt their sleep or leave them feeling burned out. If you find yourself hooked on caffeine to get through the day, constantly dragging, or in need of a lot of sleep , you may have an underactive thyroid.
You might be wondering what your thyroid has to do with your stomach, but your thyroid actually plays a role in healthy bowel function. If you feel bloated, constipated or have that heavy feeling in your stomach, your thyroid may not be functioning optimally. In this case, hypothyroidism can be ruled out. Conversely, if you experience excessive diarrhea, your thyroid may be overactive and hyperthyroidism should be considered.
Hair and Skin Changes
Fertility Issues, Miscarriages and Menstrual Cycle Changes
Whenever one hormone is disrupted, there is often a disruption to other hormones up or down stream. If you are still menstruating, heavy, more frequent, or more painful periods can be a sign of hypothyroidism. Shorter, lighter or more infrequent menstruation may accompany hyperthyroidism.
How Long Does It Take To Recover From Thyroid Surgery
It will take your body a few weeks to recover after your thyroid is surgically removed . During this time you should avoid a few things, including:
- Submerging your incision under water.
- Lifting an object thats heavier than 15 pounds.
- Doing more than light exercise.
This generally lasts for about two weeks. After that, you can return to your normal activities.
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What Do The Results From My Thyroid Function Test Mean
Your doctor will discuss the results of your thyroid function test with you.An abnormal TSH usually indicates a deficiency or an excess of thyroid hormones available to your body, but it does not indicate why this is happening. An abnormal TSH result is usually followed by additional testing of FT3 and/or FT4 to investigate the cause.A high TSH result:
- often means an underactive thyroid gland
- can also occur;if you have an underactive thyroid gland and are receiving too little thyroid hormone medication
- can indicate in rare cases a problem with your pituitary gland, such as a tumour.
A low TSH result:
- can indicate an overactive thyroid gland or damage to your pituitary gland that prevents it from producing TSH
- can also occur if you have an underactive thyroid gland and are receiving too much thyroid hormone medication.
Whats Included In A Full Thyroid Panel
A full thyroid panel usually checks thyroid-stimulating hormone , triiodothyronine , and thyroxine levels. In some cases, a blood test for thyroid function will also check your bloodâs level of TPO antibodies. If you have abnormal thyroid hormone levels, high levels of TPO antibodies can point to an autoimmune thyroid disease as a possible reason for those abnormal levels.
Do I Have To Fast For A Thyroid Blood Test
Studies have shown that early morning fasting causes higher TSH levels compared to tests taken in the afternoon on patients that did not fast. Since fasting affect TSH levels, fasting might make it difficult to diagnose subclinical hypothyroidism, as the condition is diagnosed by specifically looking at TSH levels.5 Ask your healthcare provider whether you should fast before taking your thyroid blood test.
1. ADAM. “Everything That You Need To Know Before Getting A Full Thyroid Panel.” ThyroMate. ThyroMate.com, April 25, 2017, . Accessed April 3, 2018.
2. Luo, Elaine K. “Thyroid Function Tests.” healthline. Healthline Media, February 27, 2018, . Accessed April 3, 2018.
3. Mayo Clinic Staff. “Hypothyroidism .” MayoClinic.org. . Published December 6, 2017. Accessed April 3, 2018.
4. Northrup, Christiane. “What is Thyroid Disease? Common Thyroid Disease Symptoms To Look For.” Christiane Northrup, M.D. Christiane Northrup, October 24, 2017, . Accessed April 3, 2018.
7. “Thyroid Blood Tests.” Cleveland Clinic. The Cleveland Clinic Foundation, . Accessed April 3, 2018.
What Is A Thyroid Function Test
A thyroid function test is a blood test to check the levels of the hormones made by your thyroid gland. The test also checks the level of a hormone made by the pituitary gland in your brain, which acts on your thyroid gland.
The two hormones, thyroxine and thyroid-stimulating hormone , work together and are usually in balance. In a healthy person the brain produces just the right amount of TSH to keep the thyroid gland ticking over. The thyroid gland then produces just the right amount of thyroxine.
This is called a feedback loop: if the thyroid gland makes too much thyroxine it will feed back to the brain to make less TSH. This diagram shows the feedback loop between the thyroid gland in your neck and the pituitary gland in the brain:
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What Should Be Tested
A full thyroid panel is required to obtain the most comprehensive and accurate look at how youre doing, as TSH alone and even TSH and Free T4 test without the other components of the thyroid panel, dont give the full picture.
Free T3 and Thyroid Antibodies TpoAB and TgAB are important to monitor too. Many thyroid patients find that whilst their TSH is OK, their Free T3 and Free T4, or even Reverse T3 isnt;optimal and so they still feel unwell. If your doctor wont order the full thyroid panel, do know that it is relatively inexpensive and simple to order these tests yourself. UK thyroid patients can order them from;here;and a worldwide link can be seen;here.
TSH serves as an average read out over the previous four to six weeks of your thyroid levels but doesnt give the most comprehensive view.
How Much Does The Test Cost
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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Free Levels Vs Total Levels Of T3 And T4
If you noticed, the tests done in the study were free levels of T3 and T4. The cheaper test, and more commonly done, is total T4. Measuring the free levels of hormone in your blood means we are measuring how much is available to work on the cellular level.
Total levels of hormone are a combination of free levels and bound levels. You see, most of the hormones are bound by proteins to carry them around in the bloodstream, so they can be available at distant sites. When the free hormone is used by a cell, the binding protein can release another hormone so it is then available. The binding of the hormone is a complex deal that is affected by other circulating hormones, such as estrogen.
Thyroxine Triiodothyronine And Tsh Levels
The main job of the thyroid gland is to make the hormone thyroxine, also known as T4 because it has four iodine molecules. The thyroid also makes the hormone triiodothyronine, known as T3 because it has three iodine molecules, but in smaller amounts, explains Cathy Doria-Medina, MD, an endocrinologist with HealthCare Partners Medical Group in Torrance, California. The thyroid gland makes mostly T4, the T4 has to be converted to T3, because T3 is the part of thyroxine that actually does the work, she says.
The pituitary gland at the base of the brain controls hormone production in your body. It makes thyroid-stimulating hormone , which tells the thyroid gland how much T4 and T3 to produce. The TSH level in your blood reveals how much T4 your pituitary gland is asking your thyroid gland to make. If your TSH levels are abnormally high, it could mean you have an underactive thyroid, or hypothyroidism. Thats because it indicates your pituitary gland is producing more TSH in an effort to stimulate your thyroid to produce thyroid hormone, according to the Mayo Clinic.
TSH levels go in the opposite direction of your thyroid hormone, Dr. Doria-Medina explains. If youre making too little thyroid hormone, your TSH will go up. If youre making too much thyroid hormone, your TSH will go down.
If your TSH is higher than 4.0 mU/L on repeat tests, you probably have hypothyroidism.