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Thyroid Function Tests | American Thyroid Association

WHAT IS THE THYROID GLAND?

The thyroid gland is a butterfly-shaped endocrine gland that is normally located in the lower front of the neck. The thyroid’s job is to make thyroid hormones, which are secreted into the blood and then carried to every tissue in the body. Thyroid hormones help the body use energy, stay warm and keep the brain, heart, muscles, and other organs working as they should.

HOW DOES THE THYROID GLAND FUNCTION?

The major thyroid hormone secreted by the thyroid gland is thyroxine, also called T4 because it contains four iodine atoms. To exert its effects, T4 is converted to triiodothyronine (T3) by the removal of an iodine atom. This occurs mainly in the liver and in certain tissues where T3 acts, such as in the brain. The amount of T4 produced by the thyroid gland is controlled by another hormone, which is made in the pituitary gland located at the base of the brain, called thyroid stimulating hormone (abbreviated TSH). The amount of TSH that the pituitary sends into the bloodstream depends on the amount of T4 that the pituitary sees. If the pituitary sees very little T4, then it produces more TSH to tell the thyroid gland to produce more T4. Once the T4 in the bloodstream goes above a certain level, the pituitary’s production of TSH is shut off. In fact, the thyroid and pituitary act in many ways like a heater and a thermostat. When the heater is off and it becomes cold, the thermostat reads the temperature and turns on the heater. When the heat rises to an appropriate level, the thermostat senses this and turns off the heater. Thus, the thyroid and the pituitary, like a heater and thermostat, turn on and off. This is illustrated in the figure below.

T4 and T3 circulate almost entirely bound to specific transport proteins. If the levels of these transport proteins changes, there can be changes in how much bound T4 and T3 is measured. This frequently happens during pregnancy and with the use of birth control pills. The “free” T4 or T3 is the hormone that is unbound and able to enter and affect the body tissues.

TESTS

Blood tests to measure these hormones are readily available and widely used, but not all are useful in all situations. Tests to evaluate thyroid function include the following:

TSH TESTS
The best way to initially test thyroid function is to measure the TSH level in a blood sample. Changes in TSH can serve as an “early warning system” – often occurring before the actual level of thyroid hormones in the body becomes too high or too low. A high TSH level indicates that the thyroid gland is not making enough thyroid hormone (primary hypothyroidism). The opposite situation, in which the TSH level is low, usually indicates that the thyroid is producing too much thyroid hormone (hyperthyroidism). Occasionally, a low TSH may result from an abnormality in the pituitary gland, which prevents it from making enough TSH to stimulate the thyroid (secondary hypothyroidism). In most healthy individuals, a normal TSH value means that the thyroid is functioning properly.

T4 TESTS
T4 is the main form of thyroid hormone circulating in the blood. A Total T4 measures the bound and free hormone and can change when binding proteins differ (see above). A Free T4 measures what is not bound and able to enter and affect the body tissues. Tests measuring free T4 – either a free T4 (FT4) or free T4 index (FTI) – more accurately reflect how the thyroid gland is functioning when checked with a TSH.

The finding of an elevated TSH and low FT4 or FTI indicates primary hypothyroidism due to disease in the thyroid gland. A low TSH and low FT4 or FTI indicates hypothyroidism due to a problem involving the pituitary gland. A low TSH with an elevated FT4 or FTI is found in individuals who have hyperthyroidism.

T3 TESTS
T3 tests are often useful to diagnosis hyperthyroidism or to determine the severity of the hyperthyroidism. Patients who are hyperthyroid will have an elevated T3 level. In some individuals with a low TSH, only the T3 is elevated and the FT4 or FTI is normal. T3 testing rarely is helpful in the hypothyroid patient, since it is the last test to become abnormal. Patients can be severely hypothyroid with a high TSH and low FT4 or FTI, but have a normal T3.

FREE T3
Measurement of free T3 is possible, but is often not reliable and therefore not typically helpful.

REVERSE T3
Reverse T3 is a biologically inactive protein that is structurally very similar to T3, but the iodine atoms are placed in different locations, which makes it inactive. Some reverse T3 is produced normally in the body, but is then rapidly degraded. In healthy, non-hospitalized people, measurement of reverse T3 does not help determine whether hypothyroidism exists or not, and is not clinically useful.

THYROID ANTIBODY TESTS

The immune system of the body normally protects us from foreign invaders such as bacteria and viruses by destroying these invaders with substances called antibodies produced by blood cells known as lymphocytes. In many patients with hypothyroidism or hyperthyroidism, lymphocytes react against the thyroid (thyroid autoimmunity) and make antibodies against thyroid cell proteins. Two common antibodies are thyroid peroxidase antibody and thyroglobulin antibody. Measuring levels of thyroid antibodies may help diagnose the cause of the thyroid problem. For example, positive anti-thyroid peroxidase and/or anti-thyroglobulin antibodies in a patient with hypothyroidism result in a diagnosis of Hashimoto’s thyroiditis. While detecting antibodies is helpful in the initial diagnosis of hypothyroidism due to autoimmune thyroiditis, following their levels over time is not helpful in detecting the development of hypothyroidism or response to therapy. TSH and FT4 are what tell us about the actual thyroid function or levels.

A different antibody that may be positive in a patient with hyperthyroidism is the stimulatory TSH receptor antibody (TSI). This antibody causes the thyroid to be overactive in Graves’ Disease. If you have Graves’ disease, your doctor might also order a thyrotropin receptor antibody test (TSHR or TRAb), which detects both stimulating and blocking antibodies. Following antibody levels in Graves’ patients may help to assess response to treatment of hyperthyroidism, to determine when it is appropriate to discontinue antithyroid medication, and to assess the risk of passing antibodies to the fetus during pregnancy.

THYROGLOBULIN
Thyroglobulin (Tg) is a protein produced by normal thyroid cells and thyroid cancer cells. It is not a measure of thyroid function and it does not diagnose thyroid cancer when the thyroid gland is still present. It is used most often in patients who have had surgery for thyroid cancer in order to monitor them after treatment. Tg is included in this brochure of thyroid function tests to communicate that, although measured frequently in certain scenarios and individuals, Tg is not a primary measure of thyroid hormone function.

NON-BLOOD TESTS

RADIOACTIVE IODINE UPTAKE
Because T4 contains iodine, the thyroid gland must pull a large amount of iodine from the bloodstream in order to make an appropriate amount of T4. The thyroid has developed a very active mechanism for doing this. Therefore, this activity can be measured by having an individual swallow a small amount of iodine, which is radioactive. The radioactivity allows the doctor to track where the iodine goes. By measuring the amount of radioactivity that is taken up by the thyroid gland (radioactive iodine uptake, RAIU), doctors may determine whether the gland is functioning normally. A very high RAIU is seen in individuals whose thyroid gland is overactive (hyperthyroidism), while a low RAIU is seen when the thyroid gland is underactive (hypothyroidism). In addition to the radioactive iodine uptake, a thyroid scan may be obtained, which shows a picture of the thyroid gland and reveals what parts of the thyroid have taken up the iodine (see Thyroid Nodules brochure).

MEDICATIONS THAT INTERFERE WITH THYROID FUNCTION TESTING

There are many medications that can affect thyroid function testing. Some common examples include:

  • Estrogens, such as in birth control pills, or in pregnancy, cause high levels of total T4 and T3. This is because estrogens increase the level of the binding proteins. In these situations, it is better to ask both for TSH and free T4 for thyroid evaluation, which will typically be in the normal range.
  • Biotin, a commonly taken over-the-counter supplement, can cause the measurement of several thyroid function tests to appear abnormal, when they are in fact normal in the blood. Biotin should not be taken for 2 days before blood is drawn for thyroid function testing to avoid this effect.

Thyroid Blood Tests



Overview

What are thyroid blood tests and why are they taken?

Thyroid blood tests are used to tell if your thyroid gland is functioning properly by measuring the amount of thyroid hormones in your blood. They are done by withdrawing blood from a vein in your arm. These blood tests help to diagnose thyroid diseases.

The thyroid is a butterfly-shaped gland located in the front part of your neck. Its job is to produce thyroid hormones, which travel through your bloodstream and regulate many aspects of your body’s metabolism, including temperature, weight, and energy.

Thyroid blood tests show if you have:

  • Hyperthyroidism: Overactive thyroid producing more thyroid hormones than your body needs. Hyperthyroidism speeds up your metabolism, which can cause weight loss, rapid heartbeat, insomnia, puffiness around the eyes, anxiety and other symptoms. The most common cause of hyperthyroidism is Graves’ disease.
  • Hypothyroidism: Underactive thyroid producing too few thyroid hormones. Hypothyroidism slows down your metabolism, which can cause weight gain, menstrual irregularity, dry and puffy skin, fatigue and other symptoms. The most common cause of hypothyroidism is Hashimoto’s disease.

Thyroid blood tests are used to diagnose thyroid disorders associated with hyper- or hypothyroidism. These include:



Test Details

What blood tests are done to test the thyroid?

Thyroid blood tests include:

  • Thyroid-stimulating hormone (TSH) is produced in the pituitary gland and regulates the balance of thyroid hormones –- including T4 and T3 — in the bloodstream. This is usually the first test your provider will do to check for thyroid hormone imbalance. Most of the time, thyroid hormone deficiency (hypothyroidism) is associated with an elevated TSH level, while thyroid hormone excess (hyperthyroidism) is associated with a low TSH level. If TSH is abnormal, measurement of thyroid hormones directly, including thyroxine (T4) and triiodothyronine (T3) may be done to further evaluate the problem. Normal test range for an adult: 0.40 – 4.50 mIU/mL (milli-international units per liter of blood).
  • T4: thyroxine tests for hypothyroidism and hyperthyroidism, and used to monitor treatment of thyroid disorders. Low T4 is seen with hypothyroidism, whereas high T4 levels may indicate hyperthyroidism. Normal range for an adult: 5.0 – 11.0 ug/dL (micrograms per deciliter of blood).
  • FT4: Free T4 or free thyroxin is a method of measuring T4 that eliminates the effect of proteins that naturally bind T4 and may prevent accurate measurement. Normal test range for an adult: 0.9 – 1.7 ng/dL (nanograms per deciliter of blood)
  • T3: triiodothyronine tests help diagnose hyperthyroidism or to show the severity of hyperthyroidism. Low T3 levels can be observed in hypothyroidism, but more often this test is useful in the diagnosis and management of hyperthyroidism, where T3 levels are elevated. Normal range: 100 – 200 ng/dL (nanograms per deciliter of blood).
  • FT3: Free T3 or free triiodothyronine is a method of measuring T3 that eliminates the effect of proteins that naturally bind T3 and may prevent accurate measurement. Normal range: 2.3 – 4.1 pg/mL (picograms per milliliter of blood)

These tests alone aren’t meant to diagnose any illness but may prompt your healthcare provider to do additional testing to evaluate for a possible thyroid disorder.

Additional blood tests might include:

  • Thyroid antibodies: These tests help identify different types of autoimmune thyroid conditions. Common thyroid antibody tests include microsomal antibodies (also known as thyroid peroxidase antibodies or TPO antibodies), thyroglobulin antibodies (also known as TG antibodies), and thyroid receptor antibodies (includes thyroid stimulating immunoglobulins [TSI] and thyroid blocking immunoglobulins [TBI]).
  • Calcitonin: This test is used to diagnose C-cell hyperplasia and medullary thyroid cancer, both of which are rare thyroid disorders.
  • Thyroglobulin: This test is used to diagnose thyroiditis (thyroid inflammation) and to monitor treatment of thyroid cancer.



Results and Follow-Up

What more should I know about thyroid blood tests?

Ranges noted here are approximate; your providers’ may differ slightly. It’s 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.

Thyroid Panel Test | Lab Tests Online

Sources Used in Current Review

(2017 May. Updated). Thyroid Tests. National Institute of Diabetes and Digestive and Kidney Diseases. Available online at https://www.niddk.nih.gov/health-information/diagnostic-tests/thyroid. Accessed July 2020.

(2014). Thyroid Function Tests. American Thyroid Association. Available online at https://www.thyroid.org/wp-content/uploads/patients/brochures/FunctionTests_brochure.pdf. Accessed July 2020.

(July 2017, Updated). Hyperthyroidism. Home Health Network from the Endocrine Society. Available online at https://www.hormone.org/diseases-and-conditions/thyroid/hyperthyroidism. Accessed July 2020.

(March 2020, Updated).Straseski, J. Thyroid Disease. ARUP Consult. Available online at https://arupconsult.com/content/thyroid-disease. Accessed July 2020.

(2015 November 1, Updated). Sofronescu, A. Thyroid Screen Interpretation. Medscape Protocols. Available online at https://emedicine.medscape.com/article/2172202-overview. Accessed July 2020.

(2016 June 9). Dietrich, J. et. al. Calculated Parameters of Thyroid Homeostasis: Emerging Tools for Differential Diagnosis and Clinical Research. Front Endocrinol (Lausanne). 2016; 7: 57. Available online at https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4899439/ Accessed July 2020.

(1995–2020). Thyroid Function Cascade, Serum. Mayo Medical Laboratories. Available online at https://www.mayomedicallaboratories.com/test-catalog/Overview/83633. Accessed July 2020.

(2020). ARUP Laboratories. Thyroid Panel. Available online at https://ltd.aruplab.com/Tests/Pub/0070141. Accessed July 2020.

Sources Used in Previous Reviews

American Thyroid Association. Thyroid Function Tests, patient information. PDF available for download at http://www.thyroid.org/patients/brochures/FunctionTests_brochure.pdf. Accessed May 2008.

Pagana K, Pagana T. Mosby’s Manual of Diagnostic and Laboratory Tests. 3rd Edition, St. Louis: Mosby Elsevier; 2006.

(April 27, 2007) MedlinePlus, Medical Encyclopedia. Thyroid Function Tests. Available online at http://www.nlm.nih.gov/medlineplus/encyclopedia.html. Accessed May 2008.

Quest Diagnostics. Thyroid Function Panel. Available online through http://www.questdiagnostics.com. Accessed May 2008.

Shomon, Mary. Thyroid Blood Tests. About.com Guide. Updated: March 27, 2007. Available online at http://thyroid.about.com/od/gettestedanddiagnosed/a/bloodtests.htm. Accessed June 22, 2010.

Tietz Textbook of Clinical Chemistry and Molecular Diagnostics. Burtis CA, Ashwood ER, Bruns DE, eds. St. Louis: Elsevier Saunders; 2006, Pp. 2053, 2063-2064.

Kasper DL, Braunwald E, Fauci AS, Hauser SL, Longo DL, Jameson JL eds (2005). Harrison’s Principles of Internal Medicine, 16th Edition, McGraw Hill, Pg 2119.

ARUP Lab Tests. Thyroid Panel. Available online at http://www.aruplab.com/guides/ug/tests/0070141.jsp. Accessed February 2011.

National Endocrine and Metabolic Diseases Information Service. Thyroid Function Tests. Available online at http://endocrine.niddk.nih.gov/pubs/thyroidtests/index.htm. Accessed February 2011.

MedlinePlus Medical Encyclopedia. TSH Test. Available online at http://www.nlm.nih.gov/medlineplus/ency/article/003684.htm. Accessed February 2011.

MedlinePlus Medical Encyclopedia. T3 Test. Available online at http://www.nlm.nih.gov/medlineplus/ency/article/003687.htm. Accessed February 2011.

MedlinePlus Medical Encyclopedia. T4 Test. Available online at http://www.nlm.nih.gov/medlineplus/ency/article/003517.htm. Accessed February 2011.

MedlinePlus Medical Encyclopedia. T3RU Test. Available online at http://www.nlm.nih.gov/medlineplus/ency/article/003688.htm. Accessed February 2011.

Mosby’s Manual of Diagnostic and Laboratory Tests. Pagana and Pagana. 4th edition, Pg. 512.

(Updated 2014 May 14). Thyroid Tests. National Endocrine and Metabolic Diseases Information Service [On-line information]. Available online at http://endocrine.niddk.nih.gov/pubs/thyroidtests/index.aspx. Accessed January 2015.

(2012 June 4). Thyroid Function Tests. American Thyroid Association [On-line information]. Available online at http://www.thyroid.org/blood-test-for-thyroid/. Accessed January 2015.

(© 1995–2015). Thyroid Function Cascade, Serum. Mayo Clinic Mayo Medical Laboratories [On-line information]. Available online at http://www.mayomedicallaboratories.com/test-catalog/Overview/83633. Accessed January 2015.

Meikle, A. W. and Straseski, J. (Updated 2014 July). Thyroid Disease. ARUP Consult [On-line information]. Available online at http://www.arupconsult.com/Topics/ThyroidDz.html?client_ID=LTD. Accessed January 2015.

Clarke, W., Editor (© 2011). Contemporary Practice in Clinical Chemistry 2nd Edition: AACC Press, Washington, DC. Pp 431-449.

Thyroid Blood Test Results: Understanding TSH Levels

If there’s a bright side to hypothyroidism, or an underactive thyroid, it’s that treatment usually just involves taking daily medication, and testing is limited to a simple blood test. Your hypothyroidism test results are your doctor’s blueprint for prescribing the right dose of synthetic thyroid hormone medication and tracking how well it’s working.

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, [and] 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 (TSH), 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. That’s 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 you’re making too little thyroid hormone, your TSH will go up. If you’re making too much thyroid hormone, your TSH will go down.”

What’s normal can vary depending on a number of factors, including the laboratory where your blood test is done, she adds. A normal range for TSH in most laboratories is 0.4 milliunits per liter (mU/L) to 4.0 mU/L.

If your TSH is higher than 4.0 mU/L on repeat tests, you probably have hypothyroidism.

Your doctor may also order a T4 test. Most of the T4 in your blood attaches to a protein, and when it does, it can’t get into your cells. Only T4 that is unattached or “free” can get into your cells to go to work. A blood test can measure how much free T4 if available.

Hypothyroidism Tests: A Measure of Treatment Success

Hypothyroidism is treated with daily medication. Taking synthetic thyroid hormone medication can bring your T4 and TSH levels back to their normal ranges. Once you’re on the right dose, your symptoms should subside.

When you first start taking medication, your doctor will need to monitor your blood to fine-tune the dosage. “Initially you will need to be tested more frequently,” Doria-Medina says. “A person who is newly diagnosed and taking medication for hypothyroidism should be tested every six weeks until the dosage is just right.”

The dose you start with is your doctor’s educated guess about what’s best for you — most likely the lowest dose possible to avoid side effects, which can include a rapid heartbeat and restlessness.

Medication for hypothyroidism is slow acting, and it can take several weeks for your body to adjust. If your TSH is still high and your symptoms haven’t subsided after 6 to 10 weeks, your doctor will likely increase the dose, and you’ll need your blood tested again after another 6 to 10 weeks.

How to Keep Hypothyroidism Under Control

Because you’ll need to take thyroid medication every day for the rest of your life, even after the right dose is found, your hormone levels will be monitored regularly to be sure that your treatment is working properly. “Eventually, most people with hypothyroidism can just be seen yearly by their doctor,” Doria-Medina says.

The American Thyroid Association recommends that you keep your TSH within a narrow range of 0.5 to 2.5 mU/L, but don’t be alarmed if your test results vary a little. Some variation is normal because your pituitary gland sends out TSH in pulses, not a steady stream. Also, factors like the time of day you’re tested can make a difference. TSH levels are likely to be higher at night and lower during the day. Some people, including those who are pregnant or those with a history of thyroid cancer, have different TSH goals. Talk to your doctor about the target TSH range that’s right for you.

If you have new or worsening symptoms or your health status changes — such as if you become pregnant, go through menopause, or are given another medicine that can interfere with the absorption of your thyroid hormones, such as anticonvulsants, certain antacids, or iron or calcium supplements — you should see your doctor and have your blood tested again, even if it’s ahead of schedule.

Hypothyroidism – Diagnosis and treatment

Diagnosis

In general, your doctor may test for an underactive thyroid if you are feeling increasingly tired, have dry skin, constipation and weight gain, or have had previous thyroid problems or a goiter.

Blood tests

Diagnosis of hypothyroidism is based on your symptoms and the results of blood tests that measure the level of TSH and sometimes the level of the thyroid hormone thyroxine. A low level of thyroxine and high level of TSH indicate an underactive thyroid. That’s because your pituitary produces more TSH in an effort to stimulate your thyroid gland into producing more thyroid hormone.

Doctors can diagnose thyroid disorders much earlier than in the past — often before you experience symptoms. Because the TSH test is the best screening test, your doctor will likely check TSH first and follow with a thyroid hormone test if needed.

TSH tests also play an important role in managing hypothyroidism. They help your doctor determine the right dosage of medication, both initially and over time.

In addition, TSH tests are used to help diagnose a condition called subclinical hypothyroidism, which usually causes no outward signs or symptoms. In this condition, you have normal blood levels of triiodothyronine and thyroxine, but higher than normal levels of TSH.

There are certain factors that can affect blood tests for thyroid problems. One is the blood-thinning medication called heparin. Another is biotin, a vitamin taken as a stand-alone supplement or as part of a multivitamin. Let your doctor know about any medications or supplements you take before having blood tests done.

Treatment

Standard treatment for hypothyroidism involves daily use of the synthetic thyroid hormone levothyroxine (Levo-T, Synthroid, others). This oral medication restores adequate hormone levels, reversing the signs and symptoms of hypothyroidism.

You’ll likely start to feel better soon after you start treatment. The medication gradually lowers cholesterol levels elevated by the disease and may reverse any weight gain. Treatment with levothyroxine will likely be lifelong, but because the dosage you need may change, your doctor is likely to check your TSH level every year.

Determining proper dosage may take time

To determine the right dosage of levothyroxine initially, your doctor generally checks your level of TSH after six to eight weeks. After that, blood levels are generally checked six months later. Excessive amounts of the hormone can cause side effects, such as:

  • Increased appetite
  • Insomnia
  • Heart palpitations
  • Shakiness

If you have coronary artery disease or severe hypothyroidism, your doctor may start treatment with a smaller amount of medication and gradually increase the dosage. Progressive hormone replacement allows your heart to adjust to the increase in metabolism.

Levothyroxine causes virtually no side effects when used in the appropriate dose and is relatively inexpensive. If you change brands, let your doctor know to ensure you’re still receiving the right dosage.

Also, don’t skip doses or stop taking the drug because you’re feeling better. If you do, the symptoms of hypothyroidism will gradually return.

Proper absorption of levothyroxine

Certain medications, supplements and even some foods may affect your ability to absorb levothyroxine. Talk to your doctor if you eat large amounts of soy products or a high-fiber diet or you take other medications, such as:

  • Iron supplements or multivitamins that contain iron
  • Aluminum hydroxide, which is found in some antacids
  • Calcium supplements

Levothyroxine is best taken on an empty stomach at the same time every day. Ideally, you’ll take the hormone in the morning and wait an hour before eating or taking other medications. If you take it at bedtime, wait four hours after your last meal or snack.

If you miss a dose of levothyroxine, take two pills the next day.

Subclinical hypothyroidism

If you have subclinical hypothyroidism, discuss treatment with your doctor. For a relatively mild increase in TSH, you probably won’t benefit from thyroid hormone therapy, and treatment could even be harmful. On the other hand, for a higher TSH level, thyroid hormones may improve your cholesterol level, the pumping ability of your heart and your energy level.

More Information

Show more related information

Alternative medicine

Although most doctors recommend synthetic thyroxine, natural extracts containing thyroid hormone derived from the thyroid glands of pigs are available. These products contain both thyroxine and triiodothyronine. Synthetic thyroid medications contain thyroxine only, and the triiodothyronine your body needs is derived from the thyroxine.

Extracts are available by prescription only and shouldn’t be confused with the glandular concentrates sold in natural foods stores. These products aren’t regulated by the Food and Drug Administration, and their potency and purity isn’t guaranteed.

Preparing for your appointment

You’ll likely start by seeing your family doctor or a general practitioner. In some cases, you may be referred to a doctor who specializes in the body’s hormone-secreting glands (endocrinologist). Infants with hypothyroidism need immediate referral to a pediatrics endocrinologist for treatment. Children or teens need to see a pediatric endocrinologist if there is any uncertainly about starting levothyroxine or proper dosing of the hormone.

Here’s some information to help you get ready for your appointment and know what to expect from your doctor.

What you can do

  • Be aware of any pre-appointment restrictions. At the time you make the appointment, be sure to ask if there’s anything you need to do in advance.
  • Write down any symptoms you’re experiencing, including any that may seem unrelated to the reason for which you scheduled the appointment.
  • Write down key personal information, including any major stresses or recent life changes.
  • Make a list of all medications, vitamins or supplements you’re taking.
  • Take a family member or friend along, if possible. Someone who accompanies you may remember something that you missed or forgot.
  • Write down questions to ask your doctor.

Preparing a list of questions will help you make the most of your time with your doctor. For hypothyroidism, some basic questions to ask include:

  • What’s the most likely cause of my symptoms?
  • What tests do I need?
  • Is my condition likely temporary or long lasting?
  • What treatments are available, and which do you recommend?
  • I have these other health conditions. How can I best manage them together?
  • Are there restrictions I need to follow?
  • Should I see a specialist?
  • Is there a generic alternative to the medicine you’re prescribing?
  • Are there brochures or other printed material I can take with me? What websites do you recommend?

Don’t hesitate to ask any other relevant questions you have.

What to expect from your doctor

Your doctor is likely to ask you a number of questions, including:

  • When did you begin experiencing symptoms?
  • Have your symptoms been continuous or occasional?
  • How severe are your symptoms?
  • What, if anything, seems to improve your symptoms?
  • What, if anything, appears to worsen your symptoms?
  • Do you have a family history of thyroid disease?


Nov. 19, 2020

Understanding Thyroid Function Tests and Normal Ranges

Blood tests for thyroid function—TSH, total T4, free T3, TSI, and others—are an important part of diagnosing and treating thyroid disorders. While some conclusions can be drawn from a single test, a combination of test results are usually needed to establish the full nature of your thyroid health. By comparing the values of thyroid tests, a doctor can determine whether a person has hypothyroidism (low thyroid function), hyperthyroidism (overactive thyroid), or an autoimmune thyroid disease such as Graves’ disease or Hashimoto’s thyroiditis.

How to Work With Your Thyroid Medical Team

Figuring out what the various names and numbers mean can be complicated, but taking the time to learn them can help you better manage your disease.

Types of Tests

The purpose of thyroid testing is to measure the so-called “markers” of thyroid health. These are substances not only produced by the thyroid gland but other organs that regulate thyroid function. For example, the pituitary gland produces a hormone known as thyroid stimulating hormone (TSH), which regulates how much of the hormones triiodothyronine (T3) and thyroxine (T4) are produced by the thyroid gland. The interrelationship of these and other values can tell you a lot about how well or poorly your thyroid gland is functioning.

Thyroid function tests typically look at six key substances in the blood, including hormones, proteins, and immune cells known as antibodies.

© Verywell, 2018 

Thyroid Stimulating Hormone (TSH)

Thyroid stimulating hormone (TSH) is the pituitary hormone that acts as a messenger to the thyroid gland. If the pituitary gland detects that there is too little thyroid hormone in the blood, it will produce more TSH, prompting the thyroid gland to produce more thyroid hormone. When the pituitary detects too much thyroid hormone, it slows the production of TSH, signaling the thyroid gland to do the same.

Thyroxine (T4)

Thyroxine (T4) functions as a “storage” hormone. On its own, it is unable to produce energy or deliver oxygen to cells but must undergo a process known as monodeiodination in which it loses an atom of iodine to become triiodothyronine (T3). The T4 test measures two key values:

  • Total T4 is the total amount of thyroxine circulating in the blood. The includes T4 that has bonded with protein (interfering with its ability to enter certain tissue) and T4 that has not bonded to protein. 
  • Free T4 is the type not bonded to protein and is considered the active form of thyroxine.

Triiodothyronine (T3)

Triiodothyronine (T3) is the active thyroid hormone created from the conversion of thyroxine into triiodothyronine. Three different tests measure various aspects of T3:

  • Total T3 is the total amount of triiodothyronine circulating in the blood, both bound and unbound by protein.
  • Free T3 is not bound to protein and considered the active form of triiodothyronine.
  • Reverse T3 is the inactive “mirror image” of T3 that attaches to thyroid receptors but is unable to activate them.

Thyroglobulin (Tg)

Thyroglobulin (Tg) is a protein produced by the thyroid gland. It is mostly used a tumor marker to help guide thyroid cancer treatment. The aim of cancer treatment is the eradication of all cancer cells. The elevation of Tg is a sign that cancer cells are still present following thyroid removal surgery (thyroidectomy) or radioactive ablation (RAI) therapy.

By comparing baseline values with subsequent results, the Tg test can tell doctors whether the cancer treatment is working, how durable remission is, and whether there are signs of cancer recurrence.

Thyroid Antibodies

There are some thyroid disorders caused by an autoimmune disease. Autoimmune diseases occur when the immune system mistakenly targets and attacks normal cells. It does so by secreting defensive antibodies that are “matched” to receptors (antigens) on the targeted cell.

There are three common antibodies associated with autoimmune thyroid disease: 

  • Thyroid peroxidase antibodies (TPOAb) are detected in 95 percent of people with Hashimoto’s and around 70 percent of those with Graves’ disease. Elevated TPOAb is also seen, albeit less commonly, in women with postpartum thyroiditis.
  • Thyroid stimulating hormone receptor antibodies (TRAb) are seen in 90 percent of Graves’ disease cases, but only 10 percent of Hashimoto’s cases.
  • Thyroglobulin antibodies (TgAb) are produced by your body in response to the presence of thyroglobulin. They are detected in 80 percent of people with Hashimoto’s and between 50 percent to 70 percent of those with Graves’ disease. Moreover, one in four people with thyroid cancer will have elevated TgAb.

Thyroid Binding Proteins

Testing the level of proteins in the blood that binds to T3 and T4 can help doctors characterize the nature of a thyroid problem or explore conditions in which thyroid symptoms develop in people with normally functioning glands. Among the three common measures:

  • Thyroid binding globulin (TBG) measures the level of protein, known as globulin, that carries thyroid hormones in the blood. It can be measured either with electrophoresis (which uses an electrical field to measure particles) or a radioimmunoassay (which uses radioactive isotopes to measure particles).
  • T3 resin uptake (T3RU) calculates the percentage of TBG in a sample of blood.
  • Free thyroxine index (FTI) is an older method of calculation in which the total T4 is multiplied by the T3RU to characterize whether a person is hypothyroid or hyperthyroid

Test Reference Ranges

The results of any blood test will be listed alongside a reference range. The reference range is simply the expected range of values within a population.

Generally speaking, anything between the high and low ends of the reference range can be considered normal. Anything near the upper or lower limit may be considered borderline, while anything outside of the upper and lower limits would be considered abnormal.

In the middle of the reference range is a “sweet spot,” called the optimal reference range, in which thyroid function is considered ideal. 

Interpretation of Results

The interpretation of the test results can vary based on the individual and comparative values. The one test that arguably provides the most insight is the TSH. When used in combination with free T3 and free T4, the TSH can also suggest the cause of an abnormality. 

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TSH Interpretations

TSH values outside of the optimal reference range are suggestive of a thyroid disorder. Values at or near the upper or lower range may suggest a subclinical disorder (or one in which there are no observable symptoms).

According to guidelines issued by the American Association of Clinical Endocrinologists (AACE) and the American Thyroid Association (ATA), a TSH value:

  • Between 4.7 and 10 mU/L is considered subclinical hypothyroidism.
  • Over 10 mU/L is overt (symptomatic) hypothyroidism.
  • Between 0.1 and 0.5 mU/L is considered subclinical hyperthyroidism.
  • Less than 0.1 mU/L is overt hyperthyroidism.

T3 and T4 Interpretations

By comparing TSH with T4 values, your doctor may be able to better characterize the nature of a thyroid disorder. For example:

  • A normal TSH and normal T4 indicates a normally functioning thyroid gland.
  • A low TSH and high T4 generally indicates hyperthyroidism.
  • A high TSH and low T4 indicates primary hypothyroidism (due to a thyroid disease).
  • A low TSH and low T4 suggest secondary hypothyroidism (due to a disease of the pituitary gland or hypothalamus of the brain).

For diagnostic purposes, a low T3 value accompanied by a high TSH value is considered evidence of hypothyroidism. By contrast, a low TSH value accompanied by a high T3 value is considered evidence of hyperthyroidism.

Other Interpretations

The other thyroid tests may be included as part of a standard panel or ordered when needed. Some have specific aims; others are used for screening purposes or to differentiate between possible causes.

  • RT3 tests can help identify dysregulation disorders, such as euthyroid sick syndrome (ESS), in which hormone levels are abnormal, but the thyroid gland does not appear dysfunctional.
  • Tg tests, in addition to detecting cancer recurrence, can help predict the long-term outcome of treatment. According to research published in the journal Thyroid, only 4 percent of people with a thyroglobulin level under 1 will experience recurrence after five years.
  • TPOAb tests can help confirm Hashimoto’s disease if your TSH is elevated but your T4 is low.
  • TRAb tests, in addition to diagnosing Graves’ disease, may help confirm a diagnosis of toxic multinodular goiter. The test is also commonly performed during the last three months of pregnancy to evaluate the baby’s risk of being born with hyperthyroidism or Graves’ disease.
  • TgAb tests, in addition to supporting an autoimmune diagnosis, can help clarify post-cancer treatment results. This is because TgAB can interfere with Tg readings in as many as 15 percent of people with detectable TgAb. If Tg readings are low but TgABb levels are elevated, further evaluation may be needed to avoid misdiagnosis.
  • TBG tests can help determine whether the lack of the binding protein is the cause of the thyroid disorder or simply a characteristic. TBG deficiency can sometimes occur as a result of an inherited disorder, in which the thyroid gland is functioning normally but lab tests appear abnormal.
  • T3RU tests are another method of assessing TBG deficiency with higher T3RU values corresponding to lower TBG levels (and vice versa).
  • FTI tests are a reliable means of assessing thyroid function in the presence of a TBG deficiency. However, they are less commonly used today given the accuracy of newer free T3 and free T4 tests.

Controversies

There is not always consensus as to what thyroid test results mean, particularly between conventional endocrinologists and integrative medical practitioners. By and large, integrative specialists contend that the diagnostic measures endorsed by the AACE and ATA fall short in diagnosing thyroid disorders, especially in people with subclinical disease.

Even with regards to TSH testing, most integrative doctors will tell you that a TSH under 10.0 mU/L—classified as subclinical hypothyroidism—should be treated and that doing so may prevent the development of overt hypothyroidism. AACE/ATA guidelines suggest a more watch-and-wait approach.

Integrative physicians also believe that the true measure of a person’s thyroid health is the number of active hormones circulating in the blood (free T4 and free T3) and not TSH. They argue that TSH is an inexact value given that it can lie within the normal range with Hashimoto’s disease and that free T3 offers a “real-time” snapshot of thyroid function. For these practitioners, a low free T3 is considered justification for thyroid hormone replacement therapy.

By contrast, many conventional doctors will not test T3 given that there is no direct association between T3 levels and the risk of overt hypothyroidism. Moreover, the T3 replacement drug Cytomel (liothyronine) is not even endorsed for the treatment of hypothyroidism due to the risk of reactive hyperthyroidism, minimizing the value of T3 in directing thyroid treatment.

The same argument has extended to RT3 testing for which integrative practitioners believe an elevated RT3 or an imbalance in the RT3/T3 ratio is a clear sign of hypothyroidism. Research shows that there is little credible evidence that either of these claims is inherently true. 

Nor is there evidence that elevated TPOAb warrants preemptive treatment to prevent overt hypothyroidism in people suspected of having Hashimoto’s, as some might suggest.

A Word From Verywell

While there may a lack of consensus as to the interpretation of thyroid test results, most experienced endocrinologists will adhere to the principles of the AACE/ATA guidelines and use clinical judgment to individualize treatment based on your test results, symptoms, medical history, and current health.

Medical opinions can sometimes vary. The responsibility, therefore, falls on you to understand what the test results mean, to ask questions, and to find an endocrinologist willing to work with you as a full partner. If you aren’t comfortable with what you are being told, do not hesitate to seek a seek a second opinion from a qualified medical professional.

It is also important to remember that reference ranges and units of measurement used can vary from lab to lab. To ensure consistency in your test results, try to use the same lab for every test.

Thyroid Tests | NIDDK

Health care professionals use thyroid tests 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 (T4) and triiodothyronine (T3). Thyroid hormones control how the body uses energy, so they affect nearly every organ in your body, even your heart.

The thyroid is a small, butterfly-shaped gland in your neck.

Thyroid tests help health care professionals diagnose thyroid diseases such as

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

What blood tests do doctors use to check thyroid function?

Doctors may order one or more blood tests to check your thyroid function. Tests may include thyroid stimulating hormone (TSH), T4, T3, and thyroid antibody tests.

Thyroid blood tests check your thyroid function.

For these tests, a health care professional will draw blood from your arm and send it to a lab for testing. Your doctor will talk to you about your test results.

TSH test

Health care professionals usually check the amount of TSH in your blood first. TSH is a hormone made in the pituitary gland that tells the thyroid how much T4 and T3 to make.

A high TSH level most often means you have hypothyroidism, or an underactive thyroid. This means that your thyroid isn’t making enough hormone. As a result, the pituitary keeps making and releasing TSH into your blood.

A low TSH level usually means you have hyperthyroidism, or an overactive thyroid. This means that your thyroid is making too much hormone, so the pituitary stops making and releasing TSH into your blood.

If the TSH test results are not normal, you will need at least one other test to help find the cause of the problem.

T

4 tests

A high blood level of T4 may mean you have hyperthyroidism. A low level of T4 may mean you have hypothyroidism.

In some cases, high or low T4 levels may not mean you have thyroid problems. If you are pregnant or are taking oral contraceptives, your thyroid hormone levels will be higher. Severe illness or using corticosteroids—medicines to treat asthma, arthritis, skin conditions, and other health problems—can lower T4 levels. These conditions and medicines change the amount of proteins in your blood that “bind,” or attach, to T4. Bound T4 is kept in reserve in the blood until it’s needed. “Free” T4 is not bound to these proteins and is available to enter body tissues. Because changes in binding protein levels don’t affect free T4 levels, many healthcare professionals prefer to measure free T4.

T

3 test

If your health care professional thinks you may have hyperthyroidism even though your T4 level is normal, you may have a T3 test to confirm the diagnosis. Sometimes T4 is normal yet T3 is high, so measuring both T4 and T3 levels can be useful in diagnosing hyperthyroidism.

Thyroid antibody tests

Measuring levels of thyroid antibodies may help diagnose an autoimmune thyroid disorder such as Graves’ disease—the most common cause of hyperthyroidism—and Hashimoto’s disease—the most common cause of hypothyroidism. Thyroid antibodies are made when your immune system attacks the thyroid gland by mistake. Your health care professional may order thyroid antibody tests if the results of other blood tests suggest thyroid disease.

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 doctor’s 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.

Ultrasound

Ultrasound of the thyroid is most often used to look for, or more closely at, thyroid nodules. Thyroid nodules are lumps in your neck. Ultrasound can help your doctor tell if the nodules are more likely to be cancerous.

For an ultrasound, you will lie on an exam table and a technician will run a device called a transducer over your neck. The transducer bounces safe, painless sound waves off your neck to make pictures of your thyroid. The ultrasound usually takes around 30 minutes.

During an ultrasound, a transducer bounces sound waves off the neck to make images of the thyroid.

Thyroid scan

Health care professionals use a thyroid scan to look at the size, shape, and position of the thyroid gland. This test uses a small amount of radioactive iodine to help find the cause of hyperthyroidism and check for thyroid nodules. Your health care professional may ask you to avoid foods high in iodine, such as kelp, or medicines containing iodine for a week before the test.

For the scan, a technician injects a small amount of radioactive iodine or a similar substance into your vein. You also may swallow the substance in liquid or capsule form. The scan takes place 30 minutes after an injection, or up to 24 hours after you swallow the substance, so your thyroid has enough time to absorb it.

During the scan, you will lie on an exam table while a special camera takes pictures of your thyroid. The scan usually takes 30 minutes or less.

Thyroid nodules that make too much thyroid hormone show up clearly in the pictures. Radioactive iodine that shows up over the whole thyroid could mean you have Graves’ disease.

Even though only a small amount of radiation is needed for a thyroid scan and it is thought to be safe, you should not have this test if you are pregnant or breastfeeding.

Radioactive iodine uptake test

A radioactive iodine uptake test, also called a thyroid uptake test, can help check thyroid function and find the cause of hyperthyroidism. The thyroid “takes up” iodine from the blood to make thyroid hormones, which is why this is called an uptake test. Your health care professional may ask you to avoid foods high in iodine, such as kelp, or medicines containing iodine for a week before the test.

For this test, you will swallow a small amount of radioactive iodine in liquid or capsule form. During the test, you will sit in a chair while a technician places a device called a gamma probe in front of your neck, near your thyroid gland. The probe measures how much radioactive iodine your thyroid takes up from your blood. Measurements are often taken 4 to 6 hours after you swallow the radioactive iodine and again at 24 hours. The test takes only a few minutes.

If your thyroid collects a large amount of radioactive iodine, you may have Graves’ disease, or one or more nodules that make too much thyroid hormone. You may have this test at the same time as a thyroid scan.

Even though the test uses a small amount of radiation and is thought to be safe, you should not have this test if you are pregnant or breastfeeding.

What tests do doctors use if I have a thyroid nodule?

If your health care professional finds a nodule or lump in your neck during a physical exam or on thyroid imaging tests, you may have a fine needle aspiration biopsy to see if the lump is cancerous or noncancerous.

For this test, you will lie on an exam table and slightly bend your neck backward. A technician will clean your neck with an antiseptic and may use medicine to numb the area. An endocrinologist who treats people with endocrine gland problems like thyroid disease, or a specially trained radiologist, will place a needle through the skin and use ultrasound to guide the needle to the nodule. Small samples of tissue from the nodule will be sent to a lab for testing. This procedure usually takes less than 30 minutes. Your health care professional will talk with you about the test result when it is available.

90,000 TSH (thyroid stimulating hormone), take the TSH test in Moscow, prices in the laboratory Invitro

Method of determination

Chemiluminescence immunoassay. The INVITRO laboratory uses third-generation test systems with an analytical sensitivity of 0.0025 mU / l (functional sensitivity of 0.01 mU / l). This level of sensitivity is especially important in the differential diagnosis of borderline hyperthyroidism, as well as for assessing the effectiveness of suppressing the pituitary secretion of TSH in nodular lesions and thyroid cancer after surgical or conservative treatment.

Study material
Blood serum

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A pituitary hormone that regulates the function of the thyroid gland.One of the most important tests in the laboratory diagnosis of thyroid diseases.

Synonyms: Thyroid Stimulating Hormone; Thyrotropin.

Thyroid-stimulating Hormone; TSH; Thyrotropin.

Brief characteristics of thyroid-stimulating hormone

TSH – hormone of the anterior pituitary gland. It activates the production and secretion of thyroid hormones (thyroid hormones), initiates cell growth and mitotic activity of thyroid cells.The synthesis and secretion of TSH is stimulated by the thyrotropin-releasing hormone of the hypothalamus in response to a decrease in the level of circulating thyroid hormones. The level of TSH is in inverse logarithmic dependence on the concentration of T4: with an increase in the level of T4, the production of TSH decreases, with a decrease in the level of T4, the production of TSH increases compensatory, which helps to maintain the concentration of thyroid hormones at the required height.

TSH secretion is influenced by various neuronal mechanisms and changes during sleep, temperature drop, nonspecific stress.Somatostatin and dopamine have an inhibitory effect on TSH secretion, norepinephrine – a stimulating one. For TSH, daily fluctuations in concentration are characteristic: the highest values ​​of TSH in the blood reach by 2-4 a.m., a high level in the blood persists until 6-8 a.m., the minimum TSH values ​​fall on 17-18 hours. The TSH reference values ​​below are applicable for outpatients between 8 and 18 hours. The normal rhythm of thyrotropin secretion is disturbed when awake at night.

Dysfunction of the thyroid gland can lead to a decrease in the production of thyroid hormones (hypothyroidism) or to their excess in the blood (hyperthyroidism / thyrotoxicosis).

Usually, to determine the function of the thyroid gland, the level of TSH is used as a screening indicator in the form of a single test or in combination with the determination of free T4.

For what purpose is the level of thyroid-stimulating hormone in the blood serum determined?

The study is one of the most important tests in the laboratory diagnosis of thyroid diseases.

What can affect the result of the study of thyroid-stimulating hormone

With clinically pronounced primary hypothyroidism (i.e., damage at the level of the thyroid gland, which leads to a decrease in its function), there is a significant increase in TSH levels against the background of low levels of thyroid hormones. In contrast, hyperthyroidism / thyrotoxicosis is characterized by a reduced or undetectable level of TSH and high levels of thyroid hormones.

Determination of the TSH level makes it possible to detect subclinical stages of thyroid diseases, when the concentration of thyroid hormones is still maintained by regulatory mechanisms within the framework of reference values.Taking thyroid hormone preparations (L-thyroxine) on the day of the test does not affect the concentration of TSH. The change in the level of TSH during the replacement therapy of hypothyroidism with L-thyroxine drugs occurs slowly (over several weeks and months). In order to control therapy and assess the effectiveness of taking the drug, it is advisable to dynamically study the TSH level not earlier than six weeks after changing the dose or type of drug.

Severe diseases not associated with pathology of the thyroid gland can cause a temporary change in the concentration of TSH.The reason may be the use of drugs or the consequences of the disease itself. Usually there is a decrease in the level of TSH in the acute phase of the disease and a slight increase in the level during recovery.

Physiological changes in TSH concentration are noted during pregnancy. High concentrations of chorionic gonadotropin (hCG), which has a certain structural similarity to TSH, can have a stimulating effect on the synthesis of thyroid hormones. In the 1st trimester of pregnancy, there is a temporary increase in the content of T4 and a decrease in the level of TSH.During the 2nd and 3rd trimesters, the TSH level returns to normal. An increased level of TSH in early pregnancy may indicate latent hypothyroidism in the mother, potentially dangerous for the development of the fetus.

Literature

Basic literature

  1. Belcevich D.G. Clinical practice guidelines for differentiated thyroid cancer, 2020. https://www.endocrincentr.ru/sites/default/files/specialists/science/clinic-recomendations/differencirovannyy_rak_shchitovidnoy_zhelezy.pdf
  2. Dedov I.I. et al. Clinical guidelines. Russian Association of Endocrinologists. Hypothyroidism 2019. https://rae-org.ru/system/files/documents/pdf/gipotireoz.proekt.klin_.rek_3.pdf
  3. Endocrinology. National leadership. Edited by Academician I.I. Dedov, Academician G.A. Melnichenko. 2nd edition, revised and enlarged. Prepared under the auspices of the Russian Association of Endocrinologists. 2019.https: //medknigaservis.ru/wp-content/uploads/2019/03/NF0013471.pdf
  4. American Thyroid Association Guidelines for Diagnosis and Management of Hyperthyroidism and Other Causes of Thyrotoxicosis. 2016.https: //endoinfo.ru/upload/iblock/1_ATA%20Hyperthyroidism%20and%20Other%20Causes%20of%20Thyrotoxicosis%202016.pdf
  5. European Thyroid Association Guideline for the Management of Graves’ Hyperthyroidism. 2018. https://endoinfo.ru/upload/iblock/2018%20European%20Thyroid%20Association%20Guideline%20for%20the%20Management%20of%20Graves%E2%80%99%20Hyperthyroidism.pdf
  6. National institute for health and care excellence. Guideline. Thyroid disease: assessment and management. Draft for consultation. 2019.https: //www.nice.org.uk/guidance/ng145/documents/draft-guideline

Blood test for TSH – thyroid stimulating hormone, Thyroid Stimulating Hormone, TSH

TSH is a hormone of the anterior pituitary gland that regulates the secretion of T3 and T4, stimulates the development of follicles in the thyroid gland. Determination of TSH is a basic test for assessing thyroid function.Thyroid stimulating hormone is the most sensitive hormone, the level of which changes before the rest in case of a malfunction of the thyroid gland, therefore blood test for TSH is mandatory included in any laboratory examination of the function of the thyroid gland.
Thyroid stimulating hormone (Thyrotropin, TSH, TSH) is synthesized by the pituitary gland. This hormone is essential for the vital functions of the body, as it regulates the function of the thyroid gland. TSH is responsible for maintaining a constant level of thyroid hormones.If levels become too low, the hypothalamus releases a hormone that activates TSH synthesis. This laboratory test examines venous blood and determines the concentration of TSH in it.

General

Changes in Thyroid Stimulating Hormone levels can be caused by pituitary dysfunction. Increased rates lead to hyperthyroidism. A low hormone level leads to the development of symptoms of hypothyroidism. Hyperthyroidism is manifested by rapid heartbeat, unreasonable weight loss, rapid fatigue, sleep disturbances, high anxiety, hand tremors and other symptoms.Hypothyroidism is characterized by increased sensitivity to low temperatures, brittle, falling hair, dry skin, edema, and more.

Deviation of the level of thyroid hormone from the norm most often indicates violations in the regulation of thyroid functions, but in order to accurately determine their causes, in most cases additional examination is required (tests for the level of thyroid hormones, ultrasound, etc.).

Disruption of TSH synthesis can also be caused by pathologies of the hypothalamus.His diseases lead to the fact that the hypothalamus synthesizes thyroliberin in abnormally high quantities or it is produced in insufficient quantities. Thyreoliberin regulates the production of TSH, so its excess or deficiency entails a violation of the TSH level. Another reason for the violation of the concentration of thyrotropin is thyroid disease. If thyroid hormones are synthesized in excessive or insufficient quantities, this entails a change in the concentration of TSH.
This test is used to assess the condition of the thyroid gland.Based on its results, thyroid dysfunctions in newborns and infertility in women are diagnosed. Also, an analysis is prescribed at regular intervals to monitor the course of therapy.

Norms of thyroid hormones

The role of hormones in human life is great. They control the work of vital organs. Violation of their balance leads to malfunctions in the body and various diseases, which can be asymptomatic at first, and then lead to very serious complications if you do not pass the tests on time.

These signs indicate that you need to check the thyroid gland:

  • Enlargement of lymph nodes

  • Decreased libido or weakening of potency in men

  • Heart disease

  • Depressive state

  • Failure in the menstrual cycle in women

  • Hair loss

  • Developmental delay (mental and physical in children).

The thyroid gland produces two hormones: thyroxine and triiodothyronine. They are responsible for many vital functions: they regulate the activity of the brain, nervous and cardiovascular systems, the gastrointestinal tract, affect reproductive function, the functioning of the mammary and gonads, and much more.

To find out if everything is in order with your thyroid gland, you need to pass only one test – TSH (thyroid stimulating hormone). It is he who controls the thyroid gland, which is why it is called regulatory. It stimulates the synthesis of other hormones – triiodothyronine (T3) and thyroxine (T4).

The content of TSH in the blood can fluctuate depending on the time of day: at 2–4 am the level of this hormone is very high, the minimum indicator occurs around 17–18 pm.

To get an accurate picture, the TSH test should be taken in the morning on an empty stomach. On the eve, you should stop smoking, drinking alcohol, eating abundant food, and you should also avoid physical and emotional overload.

If TSH is normal, the gland works well. If its level is increased, then there has been a malfunction of the thyroid gland – hypothyroidism or hyperthyroidism.

Hypothyroidism is the most common disease and dysfunction of the thyroid gland. The reason for this is the lack of iodine in the body. An inability of the thyroid gland to produce enough hormones (T4 and T3) is the most common cause of hypothyroidism, called primary hypothyroidism. Secondary hypothyroidism is much less common.

Hormone

Normal value

Total thyroxine (T4)

62-141 nmol / L

Free thyroxine

1.5-2.9 μg / 100 ml

Total triiodothyronine (T3)

1.17-2.18 nmol / L

Free triiodothyronine

0.4 ng / 100 ml

Calcitonin

5.5-28 pmol / l

Table of indicators of thyroid hormones.

Complaints with a decrease in hormones TSH:

  • Chilliness

  • Frequent fatigue, drowsiness, depression

  • Headaches, muscle and joint pain

  • Visual disturbances, ringing in the ears

  • Low temperature

  • Swelling

  • Husky voice

  • Sweating

Some symptoms of hypothyroidism can develop so slowly that the disease can continue for a long period without a diagnosis.

The reason for low TSH can also be diet, stress, inflammation of the pituitary gland.

Signs of increased concentration of thyroid hormones – hyperthyroidism or thyrotoxicosis:

  • Distraction of attention, anxiety, insomnia

  • High pressure and pulse

  • Weight loss with good appetite

  • Hair loss

  • Violation of heartbeat

  • Shortness of breath

An imbalance in TSH and other important hormones can seriously affect a person’s life.It is necessary to keep it normal. Check your hormone levels at least once a year for prevention, even when you are not worried about anything. After all, it is better to warn the disease in advance than to cure the disease itself.

MC “Sanas” – qualified doctors of the highest category who know their job “from and to”, a reasonable approach to treatment, only the latest European equipment and the convenience of the location of medical centers in different regions. If you have one or more of the symptoms of an increase or decrease in thyroid hormones described above, make an appointment with an endocrinologist.

Make an appointment with an endocrinologist

90,000 TSG analysis price from CMD. Thyroid-stimulating hormone. Blood on ttg price

Reference values ​​(standard variant):

Parameter Age, years Men Women Units
Thyroid-stimulating hormone (TSH 5 days – 1 year 0.98-5.63 mIU / L
1-6 0.64-5.76
6-11 0.51-4.82
11-14 0.53-5.27
> 14 0.40-4.00

Reference values ​​for pregnant women:

Parameter I trimester II trimester III trimester
Thyroid-stimulating hormone 0.09 – 2.8 mIU / L 0.18 – 2.81 mIU / L 0.3 – 2.92 mIU / L
Increasing values Decrease in values
  • Primary hypothyroidism of any genesis
  • Thyroid Hashimoto
  • Ectopic TSH secretion
  • Thyroid hormone resistance syndrome
  • Heavy physical activity
  • Medicines (lithium, metoclopramide, phenobarbital)
  • Secondary (central) hypothyroidism
  • Endogenous hyperthyroidism
  • Thyrotoxicosis
  • Initial stage of subacute thyroiditis
  • Overdose with thyroid hormone preparations
  • Acromegaly
  • Chronic renal failure
  • Cirrhosis of the liver
  • Medicines (acetylsalicylic acid, glucocorticoids, heparin, sulfonamides, dopamine)

We draw your attention to the fact that the interpretation of the research results, the establishment of the diagnosis, as well as the appointment of treatment, in accordance with Federal Law No. 323-FZ “On the Fundamentals of Health Protection of Citizens in the Russian Federation” dated November 21, 2011, must be performed by a doctor of the appropriate specialization.

90,000 Take a blood test TSH (thyroid stimulating hormone) in the laboratory Medical tests, prices in the laboratory KDL

TSH – thyroid stimulating hormone. A pituitary hormone that regulates the function of the thyroid gland. It is used to screen and diagnose various thyroid dysfunctions: hypothyroidism (decreased function) and hyperthyroidism (increased function).

The synthesis and secretion of TSH is stimulated by thyroliberin, a hypothalamic peptide that is produced when the level of thyroid hormones in the bloodstream is low. Elevated levels of T3 and T4 suppress TSH secretion in a classic negative feedback loop.

When is a TSH test usually prescribed?

Most often, this study is prescribed when there is a symptom of an altered thyroid function (hyper- or hypothyroidism), when changes in the thyroid gland are detected by ultrasound, to monitor treatment when taking hormonal drugs.

An analysis for TSH in women must be prescribed during pregnancy.

What exactly is determined in the analysis process?

Thyroid stimulating hormone consists of two subunits: alpha and beta. The alpha unit of the hormone is similar to the analogous subunits of LH, FSH and hCG. The beta unit of TSH is significantly different. The test system used detects the presence of the hormone TSH in the blood by the method of chemiluminescence immunoassay on microparticles.

What do the test results mean?

Decreased TSH levels are most often observed in hyperthyroidism.Graves’ disease (diffuse toxic goiter) is the most common cause of hyperthyroidism. It is a chronic autoimmune disorder that results in overproduction of thyroid hormones. As a result, patients may experience symptoms associated with hyperthyroidism, such as palpitations, weight loss, nervousness, hand tremors, redness and irritation of the eyes, and difficulty falling asleep. In response to high levels of T3 and T4, the pituitary gland produces less TSH, which leads to low levels in the blood.

If there is a decrease in the level of thyroid hormones in the thyroid gland (hypothyroidism), the person may experience symptoms such as weight gain, dry skin, regular constipation, fatigue, and poor cold tolerance. Hashimoto’s thyroiditis is the most common cause of hypothyroidism. It is a chronic autoimmune condition in which the immune system attacks the cells of the thyroid gland, causing inflammation, causing the thyroid to not produce enough hormones. According to the principle of feedback, the pituitary gland begins to produce more TSH, which is manifested by its increased level in the blood.

In rare cases, a change in the level of TSH in the blood is associated with dysfunction of the pituitary gland or hypothalamus.

Typical test lead time

Typically a TSH test result can be obtained within 1-2 days

Do I need special preparation for the analysis?

No special training required. More details about the terms of delivery can be found in the “Preparation” section. When monitoring treatment, the TSH test should be taken under similar conditions: at the same time of day.

TTG with up to 50% discount

Interpretation of research results
“TTG”

Interpretation of test results is for informational purposes only, is not a diagnosis and is not
replaces the advice of a doctor. Reference values ​​may differ from those indicated in
depending on the equipment used, the actual values ​​will be indicated on the form
results.

A blood test for TSH is in the overwhelming majority of cases a sufficient test to assess the function of the thyroid gland. Determination of the concentration of T4 (less often T3) exceeds the diagnostic value of determining the concentration of TSH only in a situation where it is necessary to assess the rapidly changing content of thyroid hormones in the body (monitoring thyrostatic therapy for toxic goiter, monitoring thyroid function in pregnant women).

When testing for TSH hormones, the lower range of concentration values ​​is of greatest interest to the clinician. Estimation of TSH concentration in low ranges is necessary:

  • For the diagnosis of thyrotoxicosis, especially subclinical.
  • For adequate monitoring of suppressive therapy with thyroid hormone preparations of various forms of goiter.
  • For differential diagnosis of true thyrotoxicosis and suppression of TSH levels that occur during pregnancy.

The most common reasons for the discrepancy between the results of the determination of TSH and free T4 with the clinical picture with a detected diffuse increase in the size of the thyroid gland:

  • Excessive therapy with thyroid hormones (the level of TSH is lowered, the level of free T4 is normal).
  • Recent correction of thyroid hormone therapy (TSH elevated, free T4 normal).
  • Taking drugs containing T3 (TSH is lowered, free T4 is normal).
  • Insufficient thyroid hormone therapy (TSH is elevated, free T4 is normal)
  • Extrathyroid pathology.
  • Taking drugs that affect the thyroid status (glucocorticoids, dopamine, etc.)
  • Total resistance to thyroid hormones (TSH increased, free T4 increased, clinical euthyroidism).
  • TSH-secreting tumors (TSH is elevated, free T4 is elevated, clinical thyrotoxicosis).

Unit: mIU / L

Reference values:

Age

TSH, mIU / l

men

women

up to 25 days

0.7 – 9.8

1.5 – 6.5

26 days – 2 years

0.7 – 5.9

1.0 – 5.7

38 years

0.3 – 5.0

0.3 – 5.0

9 – 10 years old

1.0 – 3.7

0.9 – 4.0

11 – 14 years old

0.8 – 3.9

0.7 – 3.4

15 – 17 years old

0.7 – 2.8

0.6 – 3.7

> 17 years old

0.4 – 4.0

0.4 – 4.0

pregnant women:

I trimester

0.1 – 2.5

II trimester

0.2 – 3.0

III trimester

0.3 – 3.0

Increase:

  • Primary thyroid hypofunction.
  • Subacute thyroiditis.
  • Hashimoto’s thyroiditis.
  • Tumor of the pituitary gland.
  • Ectopic secretion in breast and lung tumors.
  • Endemic goiter.
  • Thyroid cancer.

Decrease:

  • Primary thyroid hyperfunction.
  • Hypothalamic-pituitary insufficiency.
  • Itsenko-Cushing’s syndrome.
  • Tumor of the pituitary gland.
  • Injury of the pituitary gland.

90,000 Take a blood test for thyroid hormones (TSH, T3, T4) – 30% discount!

The thyroid gland produces vital hormones.They affect the functioning of the cardiovascular and nervous systems. Most diseases are a consequence of thyroid dysfunction. You should take a blood test for TTG.

TSH is a hormone produced by the pituitary gland and contributes to the normal functioning of the thyroid gland. At the slightest deviation, there is a risk of developing pathologies.

Why do you need to do the analysis?

Sends the therapist or endocrinologist for analysis. He is appointed in the following situations: