TSH and Free T4 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.

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.

TSH

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 TSH and Free T4 test contains 1 test with 2 biomarkers.

Brief Description: The TSH (Thyroid Stimulating Hormone) and Free T4 (Thyroxine) tests are common blood tests used to evaluate thyroid function. TSH is a hormone produced by the pituitary gland that signals the thyroid gland to produce and release thyroid hormones, including T4 and T3. Free T4 refers to the unbound portion of the total thyroxine hormone circulating in the blood, which is biologically active and available for use by the body's cells.

Collection Method: Blood Draw

Specimen Type: Serum

Test Preparation: Specifc to 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 a TSH and Free T4 Test May Be Ordered

Healthcare providers may order these tests for several reasons:

  1. Symptoms of Thyroid Dysfunction: When a patient presents with symptoms suggestive of hypothyroidism (such as fatigue, weight gain, and cold intolerance) or hyperthyroidism (including weight loss, palpitations, and heat intolerance).
  2. Monitoring Thyroid Replacement Therapy: In patients receiving treatment for hypothyroidism, to adjust medication dosage.
  3. Diagnosis of Thyroid Disorders: To diagnose conditions like Hashimoto's thyroiditis, Graves' disease, and other forms of thyroiditis.
  4. Screening in Specific Populations: Such as newborn screening for congenital hypothyroidism or screening in pregnant women due to the significant impact of thyroid hormones on pregnancy and fetal development.

What the TSH and Free T4 Test Checks For

The TSH and Free T4 tests measure:

  • TSH Levels: High TSH levels typically indicate underactive thyroid function (hypothyroidism), as the pituitary produces more TSH to stimulate the thyroid gland. Conversely, low TSH levels suggest overactive thyroid function (hyperthyroidism).
  • Free T4 Levels: These levels help to directly assess the amount of thyroid hormone available in the blood. Low Free T4 levels can confirm hypothyroidism, while high levels indicate hyperthyroidism, especially if TSH levels are low.

Additional Lab Tests Ordered Alongside the TSH and Free T4 Test

When a TSH (Thyroid-Stimulating Hormone) and Free T4 (Thyroxine) panel is ordered, it typically aims to evaluate thyroid function, diagnose thyroid disorders such as hypothyroidism or hyperthyroidism, and monitor treatment. To provide a comprehensive overview of thyroid health and related issues, additional tests may be included. Here are some tests commonly ordered alongside this panel:

  1. Free T3 (Triiodothyronine):

    • Purpose: To measure the level of T3, another thyroid hormone.
    • Why Is It Ordered: T3 levels can help further evaluate thyroid function, especially in hyperthyroidism, as T3 levels can be elevated even when T4 levels are normal.

  2. Thyroid Peroxidase Antibodies (TPO Antibodies):

    • Purpose: To detect antibodies against thyroid peroxidase, an enzyme involved in thyroid hormone production.
    • Why Is It Ordered: The presence of TPO antibodies can indicate autoimmune thyroid disease, such as Hashimoto's thyroiditis (leading to hypothyroidism) or Graves' disease (associated with hyperthyroidism).

  3. Thyroglobulin Antibodies (TG Antibodies):

    • Purpose: To measure antibodies against thyroglobulin, a protein in the thyroid gland.
    • Why Is It Ordered: Like TPO antibodies, TG antibodies can indicate autoimmune thyroid conditions.

  4. Complete Blood Count (CBC):

    • Purpose: To evaluate overall blood health, including red and white blood cells, and platelets.
    • Why Is It Ordered: Thyroid disorders can affect various components of the CBC, such as causing anemia in hypothyroidism.

  5. Calcium Levels:

    • Purpose: To measure the level of calcium in the blood.
    • Why Is It Ordered: Hyperthyroidism can cause elevated calcium levels, and thyroid disorders can indirectly affect parathyroid gland function.

  6. Liver Function Tests:

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

  7. Lipid Profile:

    • Purpose: To measure cholesterol and triglyceride levels.
    • Why Is It Ordered: Hypothyroidism can lead to elevated cholesterol levels, increasing the risk of cardiovascular disease.

  8. Serum Electrolytes:

    • Purpose: To measure electrolytes such as sodium, potassium, and chloride.
    • Why Is It Ordered: Severe cases of hypothyroidism or hyperthyroidism can affect electrolyte balance.

  9. Vitamin D Levels:

    • Purpose: To measure the level of Vitamin D in the blood.
    • Why Is It Ordered: There is some evidence linking Vitamin D deficiency with autoimmune thyroid diseases.

These tests, when ordered alongside a TSH and Free T4 panel, provide a thorough evaluation of thyroid health and help in diagnosing thyroid disorders, understanding their impact on overall health, and guiding treatment. The specific combination of tests will depend on the individual's symptoms, clinical presentation, and the purpose of testing (such as initial diagnosis or monitoring of known thyroid conditions).

Conditions or Diseases Requiring a TSH and Free T4 Test

These tests are crucial in diagnosing and managing a variety of thyroid-related conditions, including:

  • Hypothyroidism: Characterized by an underactive thyroid gland, leading to low levels of thyroid hormones.
  • Hyperthyroidism: Where the thyroid gland is overactive, producing too much thyroid hormone.
  • Hashimoto's Thyroiditis: An autoimmune disorder that often leads to hypothyroidism.
  • Graves' Disease: Another autoimmune condition, but it typically results in hyperthyroidism.
  • Thyroid Nodules or Goiter: To assess the impact of these conditions on thyroid function.

Usage of TSH and Free T4 Test Results by Health Care Providers

Healthcare providers use the results of TSH and Free T4 tests to:

  1. Diagnose Thyroid Disorders: These tests help in the initial diagnosis of thyroid dysfunction.
  2. Guide Treatment Plans: For patients with diagnosed thyroid disorders, test results help in determining the appropriate treatment, such as the need for thyroid hormone replacement in hypothyroidism or antithyroid medications in hyperthyroidism.
  3. Monitor Treatment Efficacy: In patients undergoing treatment for thyroid conditions, these tests are used to monitor the effectiveness of the treatment and adjust dosages as necessary.
  4. Assess Overall Health Impact: Since thyroid hormones affect various bodily functions, understanding thyroid health is crucial in the broader context of patient health management.

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