Thyroid Health - The Top 10 Thyroid Lab Tests - [SAVE 20%]



Save 20% on The Top 10 Thyroid Lab Tests

Two primary conditions require thyroid testing: hypothyroidism and hyperthyroidism. 

Hypothyroidism occurs when your thyroid isn't producing enough T3 and T4. 

  • Symptoms and signs of hypothyroidism:  Fatigue or weakness; Intolerance to cold; Muscle aches and cramps; Constipation; Weight gain or difficulty losing weight; Poor appetite; Goiter (enlarged thyroid gland); Dry, rough skin; Coarse hair or hair loss; Eye and face swelling; Irregular or heavy menstrual periods; Depression; Memory loss; Slowed thinking and mental activity; and Increased blood cholesterol levels.

Hyperthyroidism is the term for when your body produces too much thyroid hormone. 

  • Symptoms and signs of hyperthyroidism: Nervousness, tremor, agitation; Irritability; Poor concentration; Reduced menstrual blood flow in women; Racing heartbeat or palpitations; Heat intolerance; Changes in bowel habits, such as more frequent bowel movements; Enlargement of the thyroid gland; Skin thinning; Brittle hair; Increase in appetite, feeling hungry; and Sweating. 

If these symptoms sound familiar, you may have an undiagnosed thyroid disorder.

How do you find out? You can order your lab tests directly here to evaluate the health of your thyroid. In addition to the individual thyroid tests, check out the four Thyroid Health panels for added value.

 

 


  • Promotion Code:
  • TH20

  • Ferritin 457
  • Glucose 483
  • Hemoglobin A1c (HgbA1C) 496
  • Insulin 561
  • Iron and Total Iron Binding Capacity (TIBC) 7573
  • Lipid Panel 7600
  • QuestAssureD™ 25-Hydroxyvitamin D (D2, D3), LC/MS/MS 92888
  • Selenium 5507
  • T3, Free 34429
  • T4, Free 866
  • Thyroid Peroxidase and Thyroglobulin Antibodies 7260
  • TSH 899
  • Vitamin B12 (Cobalamin) 927
     

Thyroid Foundation Panel Thyroid Panel Add-On

  • Ferritin 457
  • Glucose 483
  • Hemoglobin A1c (HgbA1C) 496
  • Insulin 561
  • Iron and Total Iron Binding Capacity (TIBC) 7573
  • Lipid Panel 7600
  • QuestAssureD™ 25-Hydroxyvitamin D (D2, D3), LC/MS/MS 92888
  • Selenium 5507
  • T3, Free 34429
  • T4, Free 866
  • Thyroid Peroxidase and Thyroglobulin Antibodies 7260
  • TSH 899
  • Vitamin B12 (Cobalamin) 927

Thyroid Add-On Panel

  • Reverse T3
  • Comprehensive Metabolic Panel (CMP)
  • CBC (includes Differential and Platelets)

  • T3 Reverse (RT3), LC/MS/MS [ 90963 ]
  • T3 Total [ 859 ]
  • T3, Free [ 34429 ]
  • T4 (Thyroxine), Total [ 867 ]
  • T4, Free [ 866 ]
  • Thyroid Peroxidase and Thyroglobulin Antibodies [ 7260 ]
  • TRAb (TSH Receptor Binding Antibody) [ 38683 ]
  • TSH [ 899 ]
  • TSI (Thyroid Stimulating Immunoglobulin) [ 30551 ]
     

TH-3. Thyroid Health Most Popular
  • T3 Reverse (RT3), LC/MS/MS [ 90963 ]
  • T3 Total [ 859 ]
  • T3, Free [ 34429 ]
  • T4 (Thyroxine), Total [ 867 ]
  • T4, Free [ 866 ]
  • Thyroid Peroxidase and Thyroglobulin Antibodies [ 7260 ]
  • TSH [ 899 ]

TH-2. Thyroid Health Most Popular
  • T3 Total [ 859 ]
  • T3, Free [ 34429 ]
  • T4 (Thyroxine), Total [ 867 ]
  • T4, Free [ 866 ]
  • TSH [ 899 ]

TH-1. Thyroid Health Most Popular
  • T4, Free [ 866 ]
  • TSH [ 899 ]

T4, Free Most Popular

Description: A T4 Free test is a blood test that measures thyroxine free levels in your blood’s serum to evaluate your thyroid’s health and to screen for, diagnose, and monitor thyroid disorders such as hypothyroidism.

Also Known As: Free T4 Test, Free Thyroxine Test, FT4 Test, T4F Test, T4 Free Test, Unbound T4 Test

Collection Method: Blood Draw

Specimen Type: Serum

Test Preparation: No preparation required

When is a T4 Free test ordered?

When a person exhibits symptoms of hyperthyroidism or hypothyroidism, a free T4 test may be administered, especially if the TSH test is abnormal.

Hyperthyroidism can cause the following signs and symptoms:

  • Heart rate has increased.
  • Anxiety
  • Loss of weight
  • Sleeping problems
  • Hand tremors
  • Weakness
  • Diarrhea
  • Visual disturbances, light sensitivity
  • Puffiness around the eyes, dryness, discomfort, and, in some cases, bulging of the eyes are all possible side effects.

Hypothyroidism can cause the following symptoms:

  • gaining weight
  • Skin that is dry
  • Constipation
  • Intolerance to the cold
  • Skin that is puffy
  • Hair loss
  • Fatigue
  • Women's menstrual irregularities

When a person is being treated for a thyroid problem, free T4 testing, along with other thyroid tests, may be requested on a regular basis.

Thyroid testing will most likely be ordered early and late in the pregnancy, as well as for a period after delivery, to monitor the mother and baby in pregnant women with thyroid abnormalities.

In the United States, thyroid hormone screening is routinely performed on babies as part of newborn screening programs.

What does a T4 Free blood test check for?

The thyroid gland, a small butterfly-shaped structure that lays on the windpipe towards the bottom of the throat, produces one of two primary hormones: thyroxine. Triiodothyronine is the other primary thyroid hormone, and together they help govern the rate at which the body utilizes energy. T4 in the blood is almost entirely linked to protein. The remaining portion is free and is the hormone's biologically active form. This test determines how much free T4 is present in the blood.

A feedback loop controls T4 production. The hypothalamus releases thyrotropin releasing hormone, which encourages the pituitary gland to generate and release thyroid-stimulating hormone when the amount of T4 in the blood drops. The thyroid gland is thus stimulated to produce and/or release more T4 as a result of TSH. TSH release is blocked as T4 content in the blood rises.

T4 accounts for over 90% of thyroid hormones. The thyroid gland releases accumulated T4 into circulation when the body requires it. T4 is either free or bound to protein in the blood. The amount of free T4 in the body is just about 0.1 percent of total T4. In the liver or other tissues, T4 is converted to T3. T3, like T4, is mainly attached to protein, however the physiologically active forms of T3 and T4 are the free versions. Free T3 in circulation is 4 to 5 times more active than free T4.

Dry skin, weight gain, cold intolerance, weariness, and irregular menstruation are among signs of hypothyroidism that occur when the thyroid gland does not produce enough T4 due to thyroid malfunction or insufficient TSH. Myxedema, or severe untreated hypothyroidism, can cause heart failure, convulsions, and coma. Hypothyroidism in children can slow growth and sexual development.

When the thyroid gland generates too much T4, the rate of a person's body functions increases, resulting in hyperthyroidism symptoms such as anxiety, increased heart rate, difficulty sleeping, weight loss, puffiness and dry itchy eyes, and hand tremors.

The most prevalent causes of thyroid dysfunction are connected to autoimmune illnesses. Hyperthyroidism is caused by Graves disease, while hypothyroidism is caused by Hashimoto thyroiditis. Thyroiditis, thyroid malignancy, and excessive or insufficient TSH production can all induce hyperthyroidism or hypothyroidism. By measuring free T4, the influence of these variables on thyroid hormone synthesis can be recognized and monitored.

Lab tests often ordered with a T4 Free test:

  • TSH
  • T3 Total
  • T3 Free
  • T4 Total
  • T3 Reverse
  • T3 Uptake
  • Thyroid Peroxidase
  • Thyroglobulin Antibodies

Conditions where a T4 Free test is recommended:

  • Hyperthyroidism
  • Hypothyroidism
  • Hashimotos
  • Graves’ Disease
  • Autoimmune Diseases
  • Thyroid Cancer

How does my health care provider use a T4 Free test?

Free thyroxine tests are used to assess thyroid function and detect thyroid disorders, such as hyperthyroidism and hypothyroidism, after the thyroid stimulating hormone level has been found to be abnormal.

The thyroid gland produces T4 and another hormone called triiodothyronine. They aid in the regulation of the rate at which the body expends energy and are governed by a feedback system. TSH promotes the thyroid gland's synthesis and release of T4 and T3.

The majority of T4 and T3 in the blood is attached to protein, while just a small amount is free. Total T4, free T4, total T3, and free T3 can all be measured in blood testing. The total T4 test has been around for a long time, but it is influenced by the quantity of protein in the blood that can bind to the hormone. The active form of thyroxine, free T4, is unaffected by protein levels. Many people believe that the free T4 test is a more accurate reflection of thyroid hormone activity, and it has largely supplanted the total T4 test.

A free T4 test can be used in conjunction with or after a TSH test, and occasionally with a free T3 test to:

  • Help diagnose the cause of hyperthyroidism and hypothyroidism by detecting too much or too little thyroid hormone.
  • Differentiate between thyroid disorders.
  • Assist in the diagnosis of pituitary diseases
  • Assist in the diagnosis of infertility in women
  • In an individual with a known thyroid condition, track the effectiveness of treatment.
  • Monitor patients with pituitary disease to ensure that their thyroid is still operating, and thyroid hormone medication should be monitored if it isn't.
  • Monitor patients with thyroid cancer whose tumors respond to TSH. TSH and T4 levels will be monitored on a regular basis to ensure that adequate thyroid hormone is being administered to maintain TSH low while keeping T4 high.

In the United States, babies are routinely tested for T4 and TSH levels to rule out congenital hypothyroidism, which can lead to mental retardation if left untreated.

Thyroid abnormalities can sometimes be detected using free T4 and TSH, however professional opinions differ on who should be screened and when they should start.

Thyroid antibodies, as well as a free T4 test, may be ordered if a health practitioner suspects someone has an autoimmune-related thyroid problem.

What does my T4 Free result mean?

In general, high free T4 levels suggest an overactive thyroid gland, while low free T4 levels suggest an underactive thyroid gland. The test results are not diagnostic in and of themselves, but they will urge the health care provider to conduct additional testing to determine the reason of the excess or deficiency.

A range of temporary and chronic thyroid disorders are linked to both decreased and increased free T4 levels. A pituitary gland issue could be indicated by low free T4 levels along with a low TSH level, or by high free T4 levels combined with a high TSH.

When thyroid tests are done to monitor treatment for thyroid or pituitary diseases, the results will tell the doctor whether the treatment is working and/or if a dose adjustment is required. People with hyperthyroidism, for example, have their free T4, free T3, and TSH levels examined on a regular basis while taking anti-thyroid medicines to ensure that the drugs are effective and to reduce doses if thyroid hormone levels fall too low. TSH and free T4 levels are monitored on a frequent basis in hypothyroid patients to ensure that the correct dose of thyroid hormone is being given to bring TSH levels back to normal.

We advise having your results reviewed by a licensed medical healthcare professional for proper interpretation of your results.


TSH Most Popular

Description: A TSH test is a blood test that measures thyroid stimulating hormone levels in your blood’s serum and is used to screen for and monitor treatment of thyroid disorders such as hypothyroidism and hyperthyroidism.

Also Known As: Thyroid Stimulating Hormone Test, Thyrotropin Test, TSH test, Thyroid Test, TSH Screen Test

Collection Method: Blood Draw

Specimen Type: Serum

Test Preparation: No preparation required

When is a TSH test ordered?

When a person has symptoms of hyperthyroidism or hypothyroidism, or an enlarged thyroid gland, a doctor may order a TSH test.

Hyperthyroidism can cause the following signs and symptoms:

  • Heart rate has increased.
  • Anxiety
  • Loss of weight
  • Sleeping problems
  • Hand tremors.
  • Weakness
  • Diarrhea
  • Visual disturbances, light sensitivity
  • Puffiness around the eyes, dryness, discomfort, and, in some cases, bulging of the eyes are all possible side effects.

Hypothyroidism can cause the following signs and symptoms:

  • gaining weight
  • Skin that is dry
  • Constipation
  • Intolerance to the cold
  • Skin that is puffy
  • Hair loss is a common problem.
  • Fatigue
  • Women's menstrual irregularities

When a person is being treated for a thyroid disease, TSH may be ordered at regular intervals. The American Thyroid Association suggests waiting 6-8 weeks after changing a person's thyroid medication dose before testing their TSH level again.

In the United States, TSH screening is routinely performed on newborns shortly after birth as part of each state's newborn screening program.

What does a TSH blood test check for?

The pituitary gland, a small structure beneath the brain and beyond the sinus cavities, produces thyroid-stimulating hormone. TSH causes thyroxine and triiodothyronine to be released into the bloodstream by the thyroid gland. These thyroid hormones aid in the regulation of the body's energy usage. This test determines how much TSH is present in the blood.

The feedback mechanism that the body utilizes to maintain consistent quantities of thyroid hormones in the blood includes TSH and its regulatory hormone, thyrotropin releasing hormone, which comes from the hypothalamus. TSH synthesis by the pituitary gland increases as thyroid hormone concentrations fall. TSH stimulates the thyroid gland, a small butterfly-shaped gland that lays flat against the windpipe at the base of the throat, to produce and release T4 and T3. Thyroid production turns on and off to maintain generally steady levels of thyroid hormones in the blood when all three organs are operating regularly.

When the thyroid produces excessive amounts of T4 and T3, the affected person may have hyperthyroidism symptoms such as high heart rate, weight loss, agitation, hand tremors, itchy eyes, and difficulty sleeping. The most prevalent cause of hyperthyroidism is Graves disease. It is a chronic autoimmune condition in which the immune system creates antibodies that mimic TSH, causing the thyroid hormone to be produced in excessive levels. As a result, the pituitary gland may produce less TSH, resulting in a low blood level.

Weight gain, dry skin, constipation, cold intolerance, and weariness are all symptoms of hypothyroidism, a condition in which the thyroid produces fewer thyroid hormones. In the United States, Hashimoto thyroiditis is the most prevalent cause of hypothyroidism. It's an autoimmune disease in which the immune system attacks the thyroid, causing inflammation and destruction as well as the generation of autoantibodies. The thyroid generates low levels of thyroid hormone in Hashimoto thyroiditis. The pituitary gland may create more TSH, resulting in a high blood level.

TSH values, on the other hand, do not necessarily indicate or predict thyroid hormone levels. TSH is produced abnormally in some persons and does not work properly. Despite having normal or modestly increased TSH values, they frequently develop hypothyroidism. Thyroid hormone levels can be high or low in a variety of thyroid illnesses, regardless of the amount of TSH in the blood.

TSH levels may be elevated or lowered in rare cases due to pituitary dysfunction. In addition to pituitary dysfunction, an issue with the hypothalamus can cause hyperthyroidism or hypothyroidism.

Lab tests often ordered with a TSH test:

  • T3 Free
  • T3 Total
  • T4 Free
  • T4 Total
  • T3 Reverse
  • T3 Uptake
  • Thyroid Peroxidase
  • Thyroglobulin Antibodies
  • Thyroid Panel

Conditions where a test TSH is recommended:

  • Hyperthyroidism
  • Hypothyroidism
  • Hashimotos
  • Graves’ Disease
  • Autoimmune Diseases
  • Thyroid Cancer

Commonly Asked Questions:

How does my health care provider use a TSH test?

Thyroid function and/or symptoms of a thyroid problem, such as hyperthyroidism or hypothyroidism, are frequently assessed with the thyroid-stimulating hormone test.

The pituitary gland, a small structure beneath the brain and beyond the sinus cavities, produces TSH. It's a part of the body's feedback system that keeps the thyroid hormones thyroxine and triiodothyronine in check and helps regulate the pace at which the body burns calories.

TSH tests are typically ordered in conjunction with or before a free T4 test. A free T3 test and thyroid antibodies are two further thyroid tests that can be ordered. TSH, free T4, and free T3 are sometimes ordered as part of a thyroid panel.

TSH is used to:

  • Diagnose a thyroid issue in a patient who is experiencing symptoms.
  • Check newborns for an underactive thyroid.
  • Monitor thyroid replacement therapy.
  • Monitor treatment of hyperthyroidism that involves medication.
  • Assist women in diagnosing and monitoring infertility issues.
  • Assist in determining the pituitary gland's function
  • Screen adults for thyroid issues and diseases.

What does my TSH blood test result mean?

A high TSH level could indicate that:

  • The person being examined has an underactive thyroid gland that isn't responding well to TSH stimulation owing to acute or chronic thyroid dysfunction.
  • If a person has hypothyroidism or has had their thyroid gland removed, the dose of thyroid hormone replacement medicine may need to be changed.
  • A patient with hyperthyroidism is taking too much anti-thyroid medication, and the dosage needs to be reduced.
  • There is a problem with the pituitary gland, such as a tumor that causes TSH levels to be out of control.

A low TSH level could imply the following:

  • An overactive thyroid gland
  • Thyroid hormone prescription taken in excess by patients being treated for an underactive thyroid gland.
  • Inadequate medication in an individual being treated for hyperthyroidism; nevertheless, after successful anti-thyroid treatment, TSH production may take a time to recover. This is why the American Thyroid Association recommends testing for thyroid hormones as well as TSH levels throughout treatment.
  • The pituitary gland has been damaged, preventing it from releasing enough TSH.

An abnormal TSH result, whether high or low, suggests an excess or deficiency in the quantity of thyroid hormone available to the body, but does not pinpoint the cause for the abnormal result. Additional testing is frequently performed after an abnormal TSH test result to determine the reason of the increase or decrease.

We advise having your results reviewed by a licensed medical healthcare professional for proper interpretation of your results.


T3, Free Most Popular

Description: A T3 Free test is a blood test that measures unbound triiodothyronine levels in your blood’s serum to evaluate your thyroid’s health and to screen for, diagnose, and monitor thyroid disorders such as hyperthyroidism.

Also Known As: Free T3 Test, Free Triiodothyronine Test, FT3 Test, T3F Test, Unbound T3 Test

Collection Method: Blood Draw

Specimen Type: Serum

Test Preparation: No preparation required

When is a T3 Free test ordered?

When a person's TSH test results are abnormal, a free T3 test may be recommended. When a person has symptoms that imply hyperthyroidism, it may be requested as part of the investigational workup, especially if the free T4 level is not elevated.

The following are possible signs and symptoms:

  • Heart rate has increased.
  • Anxiety
  • Loss of weight
  • Sleeping problems
  • Hand tremors
  • Weakness
  • Diarrhea
  • Visual disturbances, light sensitivity
  • Puffiness around the eyes, dryness, discomfort, and, in some cases, bulging of the eyes are all possible side effects.

Free T3 may be ordered at regular intervals to monitor a known thyroid disease or to assess the efficacy of hyperthyroidism treatment.

What does a T3 Free test check for?

T3 is one of two key hormones produced by the thyroid gland, a small butterfly-shaped organ near the base of the throat that sits flat across the windpipe. Thyroxine is the other primary thyroid hormone, and together they help govern the rate at which the body utilizes energy. T3 in the blood is almost entirely linked to protein. The remaining portion is free and is the hormone's physiologically active form. Tests can determine the amount of free T3 or total T3 in the blood.

A feedback system controls T3 and T4 production. The hypothalamus releases thyrotropin releasing hormone when thyroid hormone levels in the blood drop, which prompts the pituitary gland to create and release thyroid-stimulating hormone. The thyroid gland is thus stimulated to create and/or release more thyroid hormones as a result of TSH. T4 is the most common thyroid hormone produced. This hormone is generally inactive, but in the liver and other tissues, it is transformed into the considerably more active T3.

If the thyroid gland produces too much T4 and T3, the person may have symptoms like uneasiness, hand tremors, weight loss, sleeplessness, and puffiness around dry, itchy eyes. The person's eyes may be unable to move normally and appear to be glaring in some circumstances. The eyeballs may also appear to bulge in some circumstances.

If the thyroid gland does not produce enough thyroid hormones, the person may experience weight gain, dry skin, lethargy, and constipation, which are all signs and symptoms of hypothyroidism and a slower metabolism. Thyroid hormone levels in the blood might be low or high due to thyroid malfunction, or in rare cases, insufficient or excessive TSH production due to a pituitary issue.

Autoimmune illnesses are the most common causes of thyroid dysfunction. Hyperthyroidism is caused by Graves disease, but it can also be caused by thyroiditis, thyroid malignancy, or high TSH production. Total T3 can be used to diagnose and monitor the impact of certain disorders on thyroid hormone production.

Lab tests often ordered with a T3 Free test:

  • TSH
  • T3 Total
  • T4 Free
  • T4 Total
  • T3 Reverse
  • T3 Uptake
  • Thyroid Peroxidase
  • Thyroglobulin Antibodies

Conditions where a T3 Free test is recommended:

  • Hyperthyroidism
  • Hypothyroidism
  • Hashimotos
  • Graves’ Disease
  • Autoimmune Diseases
  • Thyroid Cancer

How does my health care provider use a T3 Free test?

Thyroid function is measured with a free triiodothyronine test. It's usually ordered to assist identify hyperthyroidism, but it can also be used to track a person's therapy for a thyroid problem.

Thyroid hormones T3 and T4 are generated by the thyroid gland. They aid in the regulation of the rate at which the body expends energy and are governed by a feedback system. Thyroid-stimulating hormone boosts T4 and T3 synthesis and release. The liver and other tissues convert T4 into T3 as needed.

The majority of T4 and T3 in the blood is attached to protein, while just a small amount is free. Total T4, free T4, total T3, and free T3 can all be measured in blood tests.

Because the majority of T3 is coupled to protein, total T3 can be influenced by protein levels and binding ability, but free T3 is unaffected. Some professional standards, however, advocate total T3, thus either test can be used to evaluate thyroid function. To assist in diagnosing Graves disease, an autoimmune illness that is the most prevalent cause of hyperthyroidism, free T3 or total T3 may be ordered together with thyroid antibodies.

Following an abnormal TSH, a free T3 test is generally done, especially if the free T4 test is not high.

What does my T3 Free result mean?

Thyroid hormone levels that are high or low suggest a mismatch between the body's needs and supplies, but they don't inform the doctor what's causing the excess or deficiency.

If someone is being treated for hyperthyroidism with anti-thyroid medication and their free or total T3 levels are normal, the medicine is likely beneficial in treating the illness. If the free or total T3 or free T4 levels are high, the medication isn't working to address the problem, and the person may be having hyperthyroidism symptoms.

We advise having your results reviewed by a licensed medical healthcare professional for proper interpretation of your results


T4 (Thyroxine), Total Most Popular

Description: A T4 Total test is a blood test that measures thyroxine free levels in your blood’s serum to evaluate your thyroid’s health and to screen for, diagnose, and monitor thyroid disorders such as hypothyroidism.

Also Known As: Total T4 Test, Total Thyroxine Test, T4 Test, T4, T4 Total Test, Bound T4 Test

Collection Method: Blood Draw

Specimen Type: Serum

Test Preparation: No preparation required

When is a T4 Total test ordered?

When a person exhibits symptoms of hyperthyroidism or hypothyroidism, a Total T4 test may be administered, especially if a TSH test result is abnormal.

Hyperthyroidism can cause the following signs and symptoms:

  • Heart rate has increased.
  • Anxiety
  • Loss of weight
  • Sleeping problems
  • Hand tremors
  • Weakness
  • Diarrhea
  • Visual disturbances, light sensitivity
  • Puffiness around the eyes, dryness, discomfort, and, in some cases, bulging of the eyes are all possible side effects.

Hypothyroidism can cause the following symptoms:

  • gaining weight
  • Skin that is dry
  • Constipation
  • Intolerance to the cold
  • Skin that is puffy
  • Hair loss
  • Fatigue
  • Women's menstrual irregularities

When a person is being treated for a thyroid problem, Total T4 testing, along with other thyroid tests, may be requested on a regular basis.

Thyroid testing will most likely be ordered early and late in the pregnancy, as well as for a period after delivery, to monitor the mother and baby in pregnant women with thyroid abnormalities.

In the United States, thyroid hormone screening is routinely performed on babies as part of newborn screening programs.

What does a T4 Total blood test check for?

The thyroid gland, a small butterfly-shaped structure that lays on the windpipe towards the bottom of the throat, produces one of two primary hormones: thyroxine. Triiodothyronine is the other primary thyroid hormone, and together they help govern the rate at which the body utilizes energy. T4 in the blood is almost entirely linked to protein. The remaining portion is free and is the hormone's biologically active form. This test determines how much Bound T4 is present in the blood.

A feedback loop controls T4 production. The hypothalamus releases thyrotropin releasing hormone, which encourages the pituitary gland to generate and release thyroid-stimulating hormone when the amount of T4 in the blood drops. The thyroid gland is thus stimulated to produce and/or release more T4 as a result of TSH. TSH release is blocked as T4 content in the blood rises.

T4 accounts for over 90% of thyroid hormones. The thyroid gland releases accumulated T4 into circulation when the body requires it. T4 is either free or bound to protein in the blood. The amount of free T4 in the body is just about 0.1 percent of total T4. In the liver or other tissues, T4 is converted to T3. T3, like T4, is mainly attached to protein, however the physiologically active forms of T3 and T4 are the free versions. Free T3 in circulation is 4 to 5 times more active than free T4.

Dry skin, weight gain, cold intolerance, weariness, and irregular menstruation are among signs of hypothyroidism that occur when the thyroid gland does not produce enough T4 due to thyroid malfunction or insufficient TSH. Myxedema, or severe untreated hypothyroidism, can cause heart failure, convulsions, and coma. Hypothyroidism in children can slow growth and sexual development.

When the thyroid gland generates too much T4, the rate of a person's body functions increases, resulting in hyperthyroidism symptoms such as anxiety, increased heart rate, difficulty sleeping, weight loss, puffiness and dry itchy eyes, and hand tremors.

The most prevalent causes of thyroid dysfunction are connected to autoimmune illnesses. Hyperthyroidism is caused by Graves disease, while hypothyroidism is caused by Hashimoto thyroiditis. Thyroiditis, thyroid malignancy, and excessive or insufficient TSH production can all induce hyperthyroidism or hypothyroidism. By measuring Total T4, the influence of these variables on thyroid hormone synthesis can be recognized and monitored.

Note: Free T4 Index (T7) will only be calculated and reported if test code code 861 (T3 Uptake) is ordered as well.

Lab tests often ordered with a T4 Total test:

  • TSH
  • T3 Total
  • T3 Free
  • T4 Free
  • T3 Reverse
  • T3 Uptake
  • Thyroid Peroxidase
  • Thyroglobulin Antibodies

Conditions where a T4 Total test is recommended:

  • Hyperthyroidism
  • Hypothyroidism
  • Hashimotos
  • Graves’ Disease
  • Autoimmune Diseases
  • Thyroid Cancer

How does my health care provider use a T4 Total test?

Total thyroxine tests are used to assess thyroid function and detect thyroid disorders, such as hyperthyroidism and hypothyroidism, after the thyroid stimulating hormone level has been found to be abnormal.

The thyroid gland produces T4 and another hormone called triiodothyronine. They aid in the regulation of the rate at which the body expends energy and are governed by a feedback system. TSH promotes the thyroid gland's synthesis and release of T4 and T3.

The majority of T4 and T3 in the blood is attached to protein, while just a small amount is free. Total T4, free T4, total T3, and free T3 can all be measured in blood testing. The total T4 test has been around for a long time, but it is influenced by the quantity of protein in the blood that can bind to the hormone. The active form of thyroxine, free T4, is unaffected by protein levels. Many people believe that the free T4 test is a more accurate reflection of thyroid hormone activity, and it has largely supplanted the total T4 test.

A Total T4 test can be used in conjunction with or after a TSH test, and occasionally with a free T3 test to:

  • Help diagnose the cause of hyperthyroidism and hypothyroidism by detecting too much or too little thyroid hormone.
  • Differentiate between thyroid disorders.
  • Assist in the diagnosis of pituitary diseases
  • Assist in the diagnosis of infertility in women
  • In an individual with a known thyroid condition, track the effectiveness of treatment.
  • Monitor patients with pituitary disease to ensure that their thyroid is still operating, and thyroid hormone medication should be monitored if it isn't.
  • Monitor patients with thyroid cancer whose tumors respond to TSH. TSH and T4 levels will be monitored on a regular basis to ensure that adequate thyroid hormone is being administered to maintain TSH low while keeping T4 high.

In the United States, babies are routinely tested for T4 and TSH levels to rule out congenital hypothyroidism, which can lead to mental retardation if left untreated.

Thyroid abnormalities can sometimes be detected using Total T4 and TSH, however professional opinions differ on who should be screened and when they should start.

Thyroid antibodies, as well as a Total T4 test, may be ordered if a health practitioner suspects someone has an autoimmune-related thyroid problem.

What does my T4 Total result mean?

In general, high total T4 levels suggest an overactive thyroid gland, while low total T4 levels suggest an underactive thyroid gland. The test results are not diagnostic in and of themselves, but they will urge the health care provider to conduct additional testing to determine the reason of the excess or deficiency.

A range of temporary and chronic thyroid disorders are linked to both decreased and increased total T4 levels. A pituitary gland issue could be indicated by low total T4 levels along with a low TSH level, or by high total T4 levels combined with a high TSH.

When thyroid tests are done to monitor treatment for thyroid or pituitary diseases, the results will tell the doctor whether the treatment is working and/or if a dose adjustment is required. People with hyperthyroidism, for example, have their total T4, total T3, and TSH levels examined on a regular basis while taking anti-thyroid medicines to ensure that the drugs are effective and to reduce doses if thyroid hormone levels fall too low. TSH and total T4 levels are monitored on a frequent basis in hypothyroid patients to ensure that the correct dose of thyroid hormone is being given to bring TSH levels back to normal.

We advise having your results reviewed by a licensed medical healthcare professional for proper interpretation of your results.


T3 Total Most Popular

Description: A T3 Total test is a blood test that measures triiodothyronine levels in your blood’s serum to evaluate your thyroid’s health and to screen for, diagnose, and monitor thyroid disorders such as hyperthyroidism.

Also Known As: Total T3 Test, Triiodothyronine Test, T3 Test, Bound T3

Collection Method: Blood Draw

Specimen Type: Serum

Test Preparation: No preparation required

When is a T3 Total test ordered?

When a person's TSH test results are abnormal, a total T3 test may be recommended. When a person has symptoms that imply hyperthyroidism, it may be requested as part of the investigational workup, especially if the free T4 level is not elevated.

The following are possible signs and symptoms:

  • Heart rate has increased.
  • Anxiety
  • Loss of weight
  • Sleeping problems
  • Hand tremors
  • Weakness
  • Diarrhea
  • Visual disturbances, light sensitivity
  • Puffiness around the eyes, dryness, discomfort, and, in some cases, bulging of the eyes are all possible side effects.

Total T3 may be ordered at regular intervals to monitor a known thyroid disease or to assess the efficacy of hyperthyroidism treatment.

What does a T3 Total blood test check for?

T3 is one of two key hormones produced by the thyroid gland, a small butterfly-shaped organ near the base of the throat that sits flat across the windpipe. Thyroxine is the other primary thyroid hormone, and together they help govern the rate at which the body utilizes energy. T3 in the blood is almost entirely linked to protein. The remaining portion is free and is the hormone's physiologically active form. Tests can determine the amount of free T3 or total T3 in the blood.

A feedback system controls T3 and T4 production. The hypothalamus releases thyrotropin releasing hormone when thyroid hormone levels in the blood drop, which prompts the pituitary gland to create and release thyroid-stimulating hormone. The thyroid gland is thus stimulated to create and/or release more thyroid hormones as a result of TSH. T4 is the most common thyroid hormone produced. This hormone is generally inactive, but in the liver and other tissues, it is transformed into the considerably more active T3.

If the thyroid gland produces too much T4 and T3, the person may have symptoms like uneasiness, hand tremors, weight loss, sleeplessness, and puffiness around dry, itchy eyes. The person's eyes may be unable to move normally and appear to be glaring in some circumstances. The eyeballs may also appear to bulge in some circumstances.

If the thyroid gland does not produce enough thyroid hormones, the person may experience weight gain, dry skin, lethargy, and constipation, which are all signs and symptoms of hypothyroidism and a slower metabolism. Thyroid hormone levels in the blood might be low or high due to thyroid malfunction, or in rare cases, insufficient or excessive TSH production due to a pituitary issue.

Autoimmune illnesses are the most common causes of thyroid dysfunction. Hyperthyroidism is caused by Graves disease, but it can also be caused by thyroiditis, thyroid malignancy, or high TSH production. Total T3 can be used to diagnose and monitor the impact of certain disorders on thyroid hormone production.

Lab tests often ordered with a T3 Total test:

  • TSH
  • T3 Free
  • T4 Free
  • T4 Total
  • T3 Reverse
  • T3 Uptake
  • Thyroid Peroxidase
  • Thyroglobulin Antibodies

Conditions where a T3 Total test is recommended:

  • Hyperthyroidism
  • Hypothyroidism
  • Hashimotos
  • Graves’ Disease
  • Autoimmune Diseases
  • Thyroid Cancer

How does my health care provider use a T3 Total test?

Thyroid function is measured with a total triiodothyronine test. It's usually ordered to assist identify hyperthyroidism, but it can also be used to track a person's therapy for a thyroid problem.

Thyroid hormones T3 and T4 are generated by the thyroid gland. They aid in the regulation of the rate at which the body expends energy and are governed by a feedback system. Thyroid-stimulating hormone boosts T4 and T3 synthesis and release. The liver and other tissues convert T4 into T3 as needed.

The majority of T4 and T3 in the blood is attached to protein, while just a small amount is free. Total T4, free T4, total T3, and free T3 can all be measured in blood tests.

Because the majority of T3 is coupled to protein, total T3 can be influenced by protein levels and binding ability, but free T3 is unaffected. Some professional standards, however, advocate total T3, thus either test can be used to evaluate thyroid function. To assist diagnose Graves disease, an autoimmune illness that is the most prevalent cause of hyperthyroidism, free T3 or total T3 may be ordered together with thyroid antibodies.

Following an abnormal TSH, a total T3 test is generally done, especially if the free T4 test is not high.

What does my T3 Total Test result mean?

Thyroid hormone levels that are high or low suggest a mismatch between the body's needs and supplies, but they don't inform the doctor what's causing the excess or deficiency.

If someone is being treated for hyperthyroidism with anti-thyroid medication and their free or total T3 levels are normal, the medicine is likely beneficial in treating the illness. If the free or total T3 or free T4 levels are high, the medication isn't working to address the problem, and the person may be having hyperthyroidism symptoms.

We advise having your results reviewed by a licensed medical healthcare professional for proper interpretation of your results


T3 Reverse, LC/MS/MS Most Popular

Description: A RT3 test is a laboratory test that checks for Reverse T3 levels in your blood’s serum.

Also Known As: T3 Reverse test, REVT3 Test, RT3 Test, T3R Test, Reverse T3 Test, Reverse Triiodothyronine Test

Collection Method: Blood Draw

Specimen Type: Serum

Test Preparation: No preparation required

When is this test ordered?

Reverse T3 is used to identify stress on the body due to many factors including extreme dieting, surgery, liver and kidney disease, insulin dependent diabetes, serious injury, and chronic alcohol consumption.

What is being tested?

Reverse T3 is a derivative of Thyroxine T4. T4 becomes the active thyroid hormone Triiodothyronine T3 when it loses one of its iodine atoms. T4 is also converted by the body into Reverse T3, which is an inactive version of T3 that lacks T3's metabolic function. Reverse T3 is thought to be produced by the body to conserve energy during times of severe illness and stress.

Related Tests and Panels:

  • T3 Free
  • T3 Total
  • T4 Free
  • T4 Total
  • TSH
  • T3 Uptake
  • Thyroid Peroxidase
  • Thyroglobulin Antibodies

Related Conditions:

  • Hyperthyroidism
  • Hypothyroidism
  • Hashimotos
  • Graves’ Disease
  • Autoimmune Diseases
  • Thyroid Cancer
  • Kidney Disease
  • Liver Disease
  • Alcoholism
  • Stress
  • Diabetes

How is the Reverse T3 test used by my healthcare provider?

Results of a Reverse T3 test are used in combination with results of T4 tests, T3 Tests, thyroid antibodies, and TSH in assessing a patient’s symptoms and thyroid function.

What does my Reverse T3 test result mean?

High levels of T3 Reverse indicate that an excessive amount of T4 is being converted into Reverse T3 instead of active T3. This can cause signs of hypothyroidism, a thyroid condition often referred to as underactive thyroid, even when other thyroid hormones are within normal ranges. Elevated levels of RT3 levels can also be a sign of illness and stress and as the body converts more T4 into Reverse T3 when experiencing illnesses and stress.

We advise having your results reviewed by a licensed medical healthcare professional for proper interpretation of your results


Description: Thyroid Peroxidase and Thyroglobulin are blood tests used to detect thyroid antibodies to check for thyroid autoimmune disorders.

Also Known As: Thyroid Autoantibodies Test, Antithyroid Antibodies Test, Thyroid Peroxidase Antibody Test, Thyroperoxidase Antibody Test, TPO Test, Anti-TPO Test, Antithyroglobulin Antibody Test, TgAb Test

Collection Method: Blood Draw

Specimen Type: Serum

Test Preparation: No preparation required

When is a Thyroid Peroxidase and Thyroglobulin Antibodies test ordered?

When a person has irregular TSH and/or free T4 test results, symptoms of low or high thyroid hormone levels, or the appearance of a goiter, testing may be performed, especially if the reason is considered to be an autoimmune condition.

Hypothyroidism can produce a variety of symptoms, including:

  • Gaining weight
  • Fatigue
  • Skin that is dry
  • Hair loss
  • Cold intolerance
  • Constipation

Hyperthyroidism can produce symptoms such as:

  • Sweating
  • Heart rate that is quite fast
  • Anxiety
  • Tremors
  • Fatigue
  • Sleeping problems 
  • Sudden weight loss
  • Eyes that protrude

If a pregnant woman has a known autoimmune thyroid illness, or if another autoimmune disorder is suspected, one or more thyroid antibodies may be ordered early in the pregnancy and again at the end. These tests are performed to see if the newborn is at risk for thyroid problems. Thyroid antibodies can pass the placenta, causing hypothyroidism or hyperthyroidism in a newborn or developing kid.

Thyroid antibody testing may also be recommended if a person with another autoimmune condition has thyroid dysfunction symptoms and/or has reproductive problems that a healthcare provider suspects are caused by antibodies.

What does a Thyroid Peroxidase and Thyroglobulin Antibodies blood test check for?

Thyroid antibodies are antibodies that form when an individual's immune system incorrectly attacks the thyroid gland or thyroid protein components, causing chronic thyroid inflammation, tissue destruction, and/or thyroid function disruption. Specific thyroid antibodies in the blood are detected and quantified using laboratory techniques.

The thyroid gland is a tiny, butterfly-shaped gland in the throat that rests flat against the windpipe. Thyroxine and triiodothyronine, the two key hormones it generates, are critical in regulating the pace at which the body uses energy. Thyroid stimulating hormone stimulates the thyroid to generate T4 and T3 as needed by the body's feedback system. This mechanism aids in the maintenance of a reasonably constant level of thyroid hormones in the blood. Thyroid antibodies can cause chronic diseases and autoimmune disorders linked with hypothyroidism or hyperthyroidism, such as Graves disease or Hashimoto thyroiditis, when they interfere with this process.

Thyroid antibody testing includes the following:

  • Thyroid peroxidase antibody
  • Thyroglobulin antibody

Lab tests often ordered with a Thyroid Peroxidase and Thyroglobulin Antibodies test:

  • T3 Free
  • T3 Total
  • T4 Free
  • T4 Total
  • T3 Reverse
  • T3 Uptake
  • TSH

Conditions where a Thyroid Peroxidase and Thyroglobulin Antibodies test is recommended:

  • Hyperthyroidism
  • Hypothyroidism
  • Hashimotos
  • Graves’ Disease
  • Autoimmune Diseases
  • Thyroid Cancer

Commonly Asked Questions:

How does my health care provider use a Thyroid Peroxidase and Thyroglobulin Antibodies test?

Thyroid antibodies, such as thyroid peroxidase antibody, are tested to assist diagnose and differentiate autoimmune thyroid disease from other types of thyroid failure. Thyroid antibodies form when a person's immune system mistakenly targets thyroid gland or thyroid protein components, causing chronic thyroid inflammation, tissue destruction, and/or thyroid function disruption.

To aid in the diagnosis and/or monitoring of an autoimmune thyroid condition, one or more of the following tests may be used:

  • Thyroid peroxidase antibody, an antibody that targets thyroid peroxidase enzyme in the thyroid gland, can be seen in Graves disease and Hashimoto thyroiditis.
  • Thyroglobulin antibody is an antibody that targets thyroglobulin, the thyroid hormone's storage form.

These tests may be conducted to determine the reason of an enlarged thyroid or other symptoms linked to low or high thyroid hormone levels. When other thyroid test findings, such as total or free T3, free T4, and/or TSH, indicate thyroid dysfunction, testing may be done as a follow-up.

A thyroid antibody test or several thyroid antibody tests may be conducted to see if a person with an autoimmune disorder is at risk of thyroid dysfunction. Disorders like rheumatoid arthritis, systemic lupus erythematosus, and pernicious anemia can cause this.

A thyroglobulin test may be used to monitor someone who is being treated for thyroid cancer. The thyroglobulin antibody test is utilized in this scenario to see if the antibody is present in the person's blood and will interfere with the thyroglobulin level test.

What do my Thyroid Antibodies test results mean?

Negative test results show that thyroid antibodies were not detected in the blood at the time of testing, implying that symptoms are caused by anything other than autoimmune disease. However, antibodies are absent in a small number of persons with autoimmune thyroid disease. Repeat testing may be done at a later date if it is suspected that the antibodies will develop over time, as with several autoimmune illnesses.

Thyroid antibodies can be identified in a range of thyroid and autoimmune conditions, including thyroid cancer, type 1 diabetes, rheumatoid arthritis, pernicious anemia, and autoimmune collagen vascular diseases, with mild to moderately high levels.

Thyroid autoimmune disorders such as Hashimoto thyroiditis and Graves disease are usually associated with significantly elevated amounts.

Thyroid antibodies, in general, indicate the presence of an autoimmune thyroid illness, and the higher the level, the more likely it is. Antibody levels that grow over time may be more relevant than steady levels because they may suggest an increase in the severity of autoimmune illness. All of these antibodies can increase the risk of hypothyroidism or hyperthyroidism in a growing baby or infant if they are present in a pregnant mother.

If a person with thyroid cancer has thyroglobulin antibodies, the testing for thyroglobulin levels may be hampered. This could suggest that the thyroglobulin test can't be utilized as a tumor marker or to track a person's thyroid cancer progression. The presence of thyroglobulin antibodies has little effect on some testing procedures, including mass spectrometry. The thyroglobulin test can be utilized as a tumor marker when tested in these methods, regardless of whether or not thyroglobulin antibodies are present. If a method is utilized that is impacted by thyroglobulin antibodies, the antibodies' levels can be used as a tumor marker to monitor thyroid cancer. If they first remain high or fall low but then rise over time, the treatment was ineffective and the malignancy is likely to continue or recur. If the levels are dropping and/or have dropped to low or undetectable levels, the therapy is more likely to have been successful in eradicating the malignancy.

Thyroid antibodies can be found in a small percentage of patients who are otherwise healthy. The incidence of these antibodies is higher in women, increases with age, and implies an increased risk of developing thyroid illness in the future for thyroid peroxidase antibodies. If a person has a thyroid antibody but no obvious thyroid disease, the healthcare professional will monitor the person's health over time. While the majority of people will never have thyroid problems, a small percentage will.

We advise having your results reviewed by a licensed medical healthcare professional for proper interpretation of your results.


TSI stands for thyroid stimulating immunoglobulin. TSI tells the thyroid gland to swell and release excess amounts of thyroid hormone into the blood.