T3 Total Test Most Popular

The T3 Total Test test contains 1 test with 1 biomarker .

Brief Description: The T3 Total test measures the total levels of triiodothyronine (T3), a thyroid hormone, in the blood. T3 plays a vital role in regulating metabolism, growth, and development.

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

Testing Method: Immunoassay

Collection Method: Blood Draw 
Specimen: 1 mL Serum 

Test Preparation: No preparation required

When is a T3 Total test ordered?

A T3 Total test may be ordered in several situations to assess T3 levels:

1. Evaluation of Thyroid Function: If a patient presents with symptoms of thyroid dysfunction, such as fatigue, weight changes, or changes in mood, a T3 Total test may be ordered to evaluate thyroid function and assess for imbalances.

2. Assessment of Thyroid Hormone Production: T3 is produced by the conversion of thyroxine (T4) in the body. In cases where there is suspected alteration in thyroid hormone production, such as hyperthyroidism or hypothyroidism, a T3 Total test helps assess T3 levels and contributes to the overall evaluation of thyroid function.

3. Monitoring Thyroid Treatment: For individuals receiving thyroid hormone replacement therapy, a T3 Total test helps monitor the effectiveness of the treatment and ensures appropriate thyroid hormone levels.

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:

When a T3 Total test is ordered, it's often part of a broader assessment of thyroid function, especially if hyperthyroidism or hypothyroidism is suspected or being monitored. Here are some tests commonly ordered alongside a T3 Total test:

1. Thyroid-Stimulating Hormone (TSH):

   • Purpose: TSH is a pituitary hormone that regulates the production of thyroid hormones.
   • Why Is It Ordered: TSH is the primary screening test for thyroid function and can help determine whether the thyroid gland is overactive (hyperthyroidism) or underactive (hypothyroidism).

2. Free T4 (Thyroxine):

   • Purpose: To measure the unbound portion of T4, the primary hormone produced by the thyroid gland.
   • Why Is It Ordered: T4 is converted to the more active T3 in the body, and its measurement can help assess thyroid function and the body's ability to convert T4 to T3.

3. Free T3:

   • Purpose: To measure the unbound, active form of T3.
   • Why Is It Ordered: Free T3 levels can provide a more accurate indication of thyroid hormone activity, especially in hyperthyroidism, as T3 Total includes both bound and unbound forms of the hormone.

4. Thyroid Peroxidase Antibodies (TPO) and/or Thyroglobulin Antibodies (TgAb):

   • Purpose: To detect antibodies that target thyroid proteins, indicative of autoimmune thyroid diseases such as Hashimoto’s thyroiditis and Graves' disease.
   • Why Is It Ordered: The presence of these antibodies can help diagnose autoimmune thyroid conditions, which are common causes of thyroid hormone imbalances.

5. Reverse T3 (rT3):

   • Purpose: To measure the level of rT3, an inactive form of the hormone.
   • Why Is It Ordered: In some cases, especially in the context of non-thyroidal illness or "euthyroid sick syndrome," rT3 can be elevated, and its measurement can help evaluate overall thyroid function and metabolism.

6. Complete Blood Count (CBC):

   • Purpose: To provide a general overview of health and detect conditions such as anemia.
   • Why Is It Ordered: Thyroid disorders can sometimes lead to hematological changes, such as anemia or changes in white blood cell count.

7. Liver Function Tests:

   • Purpose: To assess liver function, as liver enzymes can be affected by thyroid hormone levels.
   • Why Is It Ordered: Abnormal thyroid function can impact liver enzyme levels, and liver dysfunction can affect thyroid hormone metabolism.

8. Calcium and Phosphorus:

   • Purpose: To evaluate calcium and phosphorus levels, as they can be affected by thyroid function.
   • Why Is It Ordered: Hyperthyroidism can sometimes cause elevated calcium levels, and these tests can be part of a broader metabolic assessment.

9. Sex Hormone Binding Globulin (SHBG):

   • Purpose: To measure levels of SHBG, which can be influenced by thyroid hormone levels.
   • Why Is It Ordered: Elevated levels of SHBG can be seen in hyperthyroidism, and this test can sometimes be used as an indirect marker of thyroid hormone activity.

These tests, combined with the T3 Total test, can help provide a comprehensive view of thyroid function and assist in diagnosing, monitoring, and managing thyroid disorders. The selection of these tests will depend on the individual's symptoms, medical history, and the results of initial thyroid function tests.

Conditions where a T3 Total test is recommended:

A T3 Total test is commonly ordered for:

1. Hyperthyroidism: Hyperthyroidism is a condition characterized by an overactive thyroid gland, leading to excess production of thyroid hormones. A T3 Total test helps evaluate the levels of T3 in individuals with suspected hyperthyroidism.

2. Hypothyroidism: Hypothyroidism refers to an underactive thyroid gland, resulting in insufficient production of thyroid hormones. A T3 Total test aids in assessing T3 levels in individuals with suspected hypothyroidism.

3. Monitoring Thyroid Hormone Replacement Therapy: For individuals receiving thyroid hormone replacement therapy, a T3 Total test helps monitor the effectiveness of the treatment and ensure appropriate thyroid hormone levels.

How does my healthcare provider use a T3 Total test?

Healthcare providers use the results of a T3 Total test to:

1. Evaluate Thyroid Function: Abnormal total T3 levels can indicate thyroid dysfunction, such as hyperthyroidism or hypothyroidism. The T3 Total test aids in the diagnosis and monitoring of these conditions.

2. Guide Treatment Decisions: Based on the T3 Total test results, healthcare providers can determine the appropriate treatment plan, such as adjusting thyroid hormone replacement dosages or initiating interventions for hyperthyroidism.

3. Monitor Thyroid Hormone Replacement Therapy: For individuals receiving thyroid hormone replacement therapy, the T3 Total test helps assess the overall levels of circulating thyroid hormones and ensure the effectiveness of the treatment.

By effectively utilizing the results of a T3 Total test, healthcare providers can evaluate thyroid function, guide treatment decisions, monitor thyroid hormone replacement therapy, and make informed decisions regarding patient care and interventions related to thyroid health.

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.

Thyroid Function Test Interpretation: Key Test Patterns For T3 Total, T4 Total, and TSH

The table provided is a simplified summary of common patterns seen in thyroid function testing.

• Interpretation of thyroid function tests should always be done in the context of the patient's clinical presentation, medical history, and additional diagnostic findings.

• Assay interference (e.g., heterophilic antibodies) can cause discordant results, but these are uncommon and require further investigation

Most Common Questions About the T3 Total test:

Understanding the Test

What is the T3 Total test?

The T3 Total test measures the total amount of triiodothyronine, a hormone produced by the thyroid gland, in your blood. This includes both free T3, which is available for use by cells and tissues, and bound T3, which is attached to proteins and not available for use.

Why would I need a T3 Total test?

A T3 Total test is usually ordered when you have symptoms of hyperthyroidism (overactive thyroid), such as rapid heart rate, weight loss, anxiety, and high blood pressure, and your TSH and T4 tests are not clearly diagnostic. It can also be used to monitor treatment in people with hyperthyroidism.

Interpreting the Results

What does a high T3 Total level indicate in the T3 Total test?

A high T3 Total level often indicates hyperthyroidism, a condition where the thyroid gland is overactive and produces too much thyroid hormone. This could be due to conditions such as Graves' disease, toxic nodular goiter, or thyroiditis.

What does a low T3 Total level indicate in the T3 Total test?

A low T3 Total level could indicate hypothyroidism, a condition where the thyroid gland is underactive and does not produce enough thyroid hormone. However, because T3 is typically the last test to show changes, it might also indicate a non-thyroidal illness.

The Test in Different Situations

How can the T3 Total test help if I have symptoms of thyroid disease?

The T3 Total test, when used in conjunction with other thyroid tests, can help identify if your symptoms are due to an overactive or underactive thyroid.

Can the T3 Total test be used to monitor the effectiveness of my thyroid disease treatment?

Yes, the T3 Total test can be used to monitor the effectiveness of treatment for hyperthyroidism. Your doctor will use the test results to adjust your treatment as needed.

About the Test

Can certain medications affect the results of the T3 Total test?

Yes, certain medications such as birth control pills, estrogen, steroids, and others can affect the results of the T3 Total test. It's important to let your healthcare provider know about any medications you're taking.

What factors can influence the results of the T3 Total test?

Factors that can influence T3 Total levels include your age, sex, and overall health. Pregnancy, stress, acute illness, and changes in body weight can also affect T3 levels.

Understanding the Implications

How does the T3 Total test contribute to understanding my energy levels and metabolism?

T3 is a hormone that plays a key role in managing the body's metabolism. If your T3 Total levels are abnormal, it might explain symptoms such as changes in appetite, energy levels, weight, and heart rate.

How does the T3 Total test contribute to understanding my weight issues?

Abnormal T3 Total levels can affect your metabolism, leading to changes in weight. High T3 levels can cause weight loss, even when your appetite and food intake increase, while low T3 levels can lead to weight gain or difficulty losing weight.

Risks and Precautions

Are there risks associated with having high T3 Total levels in the T3 Total test?

Yes, high T3 Total levels are often associated with hyperthyroidism, which can lead to complications such as heart problems, brittle bones, and thyrotoxic crisis, a sudden and severe worsening of symptoms.

Can the T3 Total test provide insights into my risk of developing certain diseases?

Abnormal T3 Total levels can indicate a thyroid disorder, which can be associated with a range of health issues. High T3 levels can increase the risk of conditions like atrial fibrillation and osteoporosis, while low T3 levels can be associated with fatigue, depression, and other symptoms of hypothyroidism.

Dealing with Abnormal Results

What should I do if my T3 Total test shows high levels of T3?

If your T3 Total test shows high levels of T3, it's important to consult with your healthcare provider. They can help determine the cause of the high levels and devise a treatment plan.

Are there ways to lower high T3 Total levels identified in the T3 Total test?

High T3 Total levels are usually treated by addressing the underlying cause, which is typically hyperthyroidism. Treatment options include medication, radioactive iodine therapy, and surgery.

Interpreting the Test Results

How are the results of the T3 Total test interpreted?

The results of the T3 Total test are interpreted by comparing your T3 levels to the reference range provided by the lab. Levels above or below this range can indicate a thyroid disorder or other health issue. It's important to have your results interpreted by a healthcare provider who understands your health history and symptoms.

Can I interpret the results of myT3 Total test on my own?

Interpreting medical test results on your own can be challenging, as they're often dependent on a variety of factors including your health history, other test results, and current symptoms. It's important to discuss your T3 Total test results with your healthcare provider for accurate interpretation and advice.

Relation to Other Tests

Why is the T3 Total test often done alongside other thyroid tests?

The T3 Total test is often done with other thyroid tests because it provides a more complete picture of thyroid function. While the TSH and T4 tests are typically done first, the T3 Total test can help diagnose hyperthyroidism if the first two tests are not conclusive.

How does the T3 Total test differ from the T3 Free test?

The T3 Total test measures both free T3 (not attached to proteins, and therefore available for use by the body) and bound T3 (attached to proteins and not available for use). The T3 Free test only measures the amount of free T3, which can sometimes provide more accurate information about thyroid function.

Further Understanding

What is the role of T3 in the body, as evaluated by the T3 Total test?

T3 is a hormone produced by the thyroid gland that helps regulate many body processes, including metabolism, heart rate, body temperature, and growth and development. The T3 Total test helps evaluate the level of T3 to understand how well the thyroid is functioning.

How does the T3 Total test contribute to understanding my overall health?

The T3 Total test can provide insight into your overall health by assessing thyroid function. Since the thyroid plays a crucial role in various body processes, understanding its function can help provide a broader understanding of your health.

Diagnosis and Treatment

What is the next step if the T3 Total test indicates hyperthyroidism?

If the T3 Total test indicates hyperthyroidism, your healthcare provider will likely order further tests to determine the cause, such as imaging studies or antibody tests. Treatment will depend on the cause and may include medication, radiation therapy, or surgery.

What is the next step if the T3 Total test indicates hypothyroidism?

If the T3 Total test indicates hypothyroidism, your healthcare provider will likely order a T4 test to confirm the diagnosis. Treatment usually involves thyroid hormone replacement therapy.

Can the T3 Total test detect thyroid cancer?

The T3 Total test is not typically used to detect thyroid cancer. It's primarily used to assess thyroid function. If thyroid cancer is suspected, other tests such as imaging studies and biopsies are usually needed.

What role does the T3 Total test play in managing autoimmune thyroid diseases?

The T3 Total test can be useful in managing autoimmune thyroid diseases like Graves' disease and Hashimoto's thyroiditis. It can help monitor the effectiveness of treatment and adjust medication doses as needed.

What should I discuss with my healthcare provider before getting a T3 Total test?

Before getting a T3 Total test, it's important to discuss any symptoms you're experiencing, as well as your medical history and any medications you're taking. This can help your healthcare provider interpret the results accurately and determine if additional testing is needed.

Sources for Thyroid Function Table

• American Thyroid Association (ATA) Guidelines. (n.d.). Thyroid function tests. Retrieved from https://www.thyroid.org

• Brent, G. A. (2012). Mechanisms of thyroid hormone action. Journal of Clinical Investigation, 122(9), 3035–3043. https://doi.org/10.1172/JCI60047

• De Groot, L. J., Chrousos, G., Dungan, K., Feingold, K. R., Grossman, A., Hershman, J. M., ... & Weickert, M. O. (2016). Non-thyroidal illness syndrome. In Endotext. MDText.com, Inc. Retrieved from https://www.ncbi.nlm.nih.gov/books/NBK285570/

• Jonklaas, J., Bianco, A. C., Bauer, A. J., Burman, K. D., Cappola, A. R., Celi, F. S., ... & Sawka, A. M. (2014). Guidelines for the treatment of hypothyroidism: Prepared by the American Thyroid Association Task Force on Thyroid Hormone Replacement. Thyroid, 24(12), 1670–1751. https://doi.org/10.1089/thy.2014.0028

• Larsen, P. R., Davies, T. F., & Hay, I. D. (2008). The thyroid gland. In Williams Textbook of Endocrinology (11th ed., pp. 299–332). Elsevier.

• Peeters, R. P., & Visser, T. J. (2017). Metabolism of thyroid hormone. In Endotext. MDText.com, Inc. Retrieved from https://www.ncbi.nlm.nih.gov/books/NBK285545/

• U.S. National Library of Medicine. (2021). Thyroid function tests. MedlinePlus. Retrieved from https://medlineplus.gov/lab-tests/thyroid-function-tests/

• Wartofsky, L., & Dickey, R. A. (2005). The evidence for a narrower thyrotropin reference range is compelling. Journal of Clinical Endocrinology & Metabolism, 90(9), 5483–5488. https://doi.org/10.1210/jc.2005-0455

• Chopra, I. J., & Solomon, D. H. (1983). Reverse T3 in serum: A measure of tissue thyroid status. Journal of Clinical Endocrinology & Metabolism, 56(4), 803–807. https://doi.org/10.1210/jcem-56-4-803

• Hennemann, G., Docter, R., Friesema, E. C. H., de Jong, M., Krenning, E. P., & Visser, T. J. (2001). Plasma membrane transport of thyroid hormones and its role in thyroid hormone metabolism and bioavailability. Endocrine Reviews, 22(4), 451–476. https://doi.org/10.1210/edrv.22.4.0435