Free T3, Free T4 & TSH Most Popular

The following is a list of what is included in the item above. Click the test(s) below to view what biomarkers are measured along with an explanation of what the biomarker is measuring.

Also known as: Free T3, FT3, T3 Free

T3, Free

This test measures the amount of triiodothyronine, or T3, in the blood.

Also known as: Free T4, FT4, T4 Free

T4, Free

The free T4 test is not affected by protein levels. Since free T4 is the active form of thyroxine, the free T4 test is may be a more accurate reflection of thyroid hormone function.

Also known as: Thyroid Stimulating Hormone, Thyroid Stimulating Hormone (TSH), Thyrotropin


A TSH test is a lab test that measures the amount of thyroid stimulating hormone (TSH) in your blood. TSH is produced by the pituitary gland. It tells the thyroid gland to make and release thyroid hormones into the blood.



A TSH test is a lab test that measures the amount of thyroid stimulating hormone (TSH) in your blood. TSH is produced by the pituitary gland. It tells the thyroid gland to make and release thyroid hormones into the blood.


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The Free T3, Free T4 & TSH panel contains 3 tests with 6 biomarkers.

Brief Description: The Free T3, Free T4 & TSH panel is a specialized group of tests aimed at evaluating thyroid function and assessing the overall health of the thyroid gland. The thyroid is a butterfly-shaped gland located in the neck, and it plays a crucial role in the endocrine system, influencing the metabolism, growth, and development of the body. The tests in this panel measure levels of hormones produced by the thyroid and pituitary glands to offer a comprehensive picture of thyroid function.

Collection Method: Blood Draw

Specimen Type: Serum

Test Preparation: For TSH, Specimen collection after fluorescein dye angiography should be delayed for at least 3 days. For patients on hemodialysis, specimen collection should be delayed for 2 weeks.

According to the assay manufacturer Siemens: "Samples containing fluorescein can produce falsely depressed values when tested with the Advia Centaur TSH3 Ultra assay."

When and Why the Free T3, Free T4 & TSH Panel May Be Ordered

The Free T3, Free T4 & TSH panel might be ordered in several scenarios:

  1. Symptoms of Thyroid Dysfunction: If a patient presents symptoms indicative of a thyroid disorder, such as unexpected weight changes, fatigue, palpitations, or hair loss, the panel may be ordered to ascertain the cause.

  2. Monitoring Existing Thyroid Conditions: For individuals previously diagnosed with conditions like hyperthyroidism or hypothyroidism, the test helps in tracking the effectiveness of treatments and adjusting dosages if necessary.

  3. Screening: As part of a general health check-up, especially if there's a family history of thyroid disorders or if the patient has other autoimmune diseases.

  4. Pregnancy: Thyroid function can affect pregnancy outcomes. Pregnant women may be tested if they have a history of thyroid issues or present with symptoms.

What the Free T3, Free T4 & TSH Panel Checks For

  • Free T3 (Triiodothyronine): This test measures the amount of unbound T3 hormone in the bloodstream. T3 is one of the two major hormones produced by the thyroid gland and plays a role in regulating metabolism.

  • Free T4 (Thyroxine): Like Free T3, this test assesses the level of unbound T4 hormone. T4 is a precursor to T3 and is converted to T3 in the body's tissues. Measuring its levels helps in understanding how much of the hormone is available for this conversion.

  • TSH (Thyroid Stimulating Hormone): Produced by the pituitary gland in the brain, TSH regulates the production and release of T3 and T4 from the thyroid gland. If the thyroid hormones are low, the pituitary produces more TSH to stimulate the thyroid, and vice-versa.

Other Lab Tests Often Ordered Alongside the Free T3, Free T4, and TSH Panel

When a panel including Free T3 (Triiodothyronine), Free T4 (Thyroxine), and TSH (Thyroid-Stimulating Hormone) is ordered, it typically indicates a comprehensive evaluation of thyroid function. These tests together help diagnose and monitor thyroid disorders such as hypothyroidism and hyperthyroidism. To gain a complete picture of thyroid health and related conditions, additional tests may be ordered. Here are some tests commonly requested alongside this thyroid panel:

  1. Thyroid Peroxidase Antibodies (TPO Antibodies):

    • Purpose: To detect antibodies against thyroid peroxidase, an enzyme important for thyroid hormone production.
    • Why Is It Ordered: The presence of TPO antibodies can indicate autoimmune thyroid disease, such as Hashimoto's thyroiditis or Graves' disease.
  2. Thyroglobulin Antibodies (TG Antibodies):

    • Purpose: To measure antibodies against thyroglobulin, a protein involved in thyroid hormone production.
    • Why Is It Ordered: Like TPO antibodies, TG antibodies can suggest autoimmune thyroid conditions.
  3. Complete Blood Count (CBC):

    • Purpose: To assess overall blood health, including red and white blood cells, and platelets.
    • Why Is It Ordered: Thyroid disorders can impact blood cell production, leading to conditions like anemia.
  4. Calcium and Phosphorus Levels:

    • Purpose: To measure the levels of calcium and phosphorus in the blood.
    • Why Is It Ordered: Thyroid disorders can affect calcium metabolism, and abnormal levels can indicate parathyroid gland involvement or bone metabolism issues.
  5. Lipid Profile:

    • Purpose: To measure cholesterol and triglyceride levels.
    • Why Is It Ordered: Hypothyroidism can lead to increased cholesterol levels, while hyperthyroidism might lower them.
  6. Liver Function Test:

    • Purpose: To assess liver enzyme levels and overall liver function.
    • Why Is It Ordered: Thyroid hormones can affect liver function, and abnormalities might be seen in severe cases of thyroid disease.
  7. Serum Electrolytes:

    • Purpose: To measure electrolytes like sodium, potassium, and chloride.
    • Why Is It Ordered: Thyroid dysfunction can sometimes affect electrolyte balance.
  8. Cortisol:

    • Purpose: To measure cortisol levels, which can be affected by severe thyroid disease.
    • Why Is It Ordered: To assess adrenal gland function, particularly in cases of suspected secondary or tertiary hypothyroidism.
  9. Sex Hormone Binding Globulin (SHBG):

    • Purpose: To measure levels of SHBG, which can be influenced by thyroid hormones.
    • Why Is It Ordered: Elevated or decreased SHBG levels can be a secondary marker of thyroid function.

These tests, when ordered alongside a Free T3, Free T4, and TSH panel, provide a comprehensive evaluation of thyroid function and its impact on overall health. They are crucial for diagnosing thyroid disorders, assessing the extent of thyroid dysfunction, and guiding appropriate treatment strategies. The specific combination of tests will depend on the individual’s symptoms, clinical presentation, and initial test results.

Conditions or Diseases the Free T3, Free T4 & TSH Panel Can Check For

The panel can be instrumental in diagnosing various thyroid-related conditions:

  • Hyperthyroidism: Characterized by an overactive thyroid, leading to excessive production of thyroid hormones. Symptoms might include weight loss, increased heart rate, anxiety, and tremors.

  • Hypothyroidism: This is the opposite of hyperthyroidism, where the thyroid gland is underactive. Symptoms often include fatigue, weight gain, cold sensitivity, and dry skin.

  • Grave's Disease: An autoimmune disorder that causes hyperthyroidism.

  • Hashimoto's Thyroiditis: An autoimmune disorder where the body's immune system attacks the thyroid gland, leading to hypothyroidism.

  • Thyroid Nodules or Goiter: Growth or enlargement of the thyroid gland can alter its hormone production, leading to either hyperthyroidism or hypothyroidism.

By comprehensively assessing the levels of Free T3, Free T4, and TSH, healthcare professionals can determine whether the thyroid gland is functioning correctly, underactive, or overactive, and pinpoint the potential cause of the dysfunction.

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

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