TH-1. Hypothyroidism

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.


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The TH-1. Hypothyroidism panel contains 3 tests with 4 biomarkers.

Brief Description: The TH-1 Hypothyroidism panel is a focused set of laboratory tests aimed at evaluating the thyroid function. This panel includes three essential tests: T3 Free, T4 Free, and Thyroid Stimulating Hormone (TSH). Each of these tests plays a crucial role in assessing the thyroid gland's activity, which is pivotal in regulating metabolism, energy generation, and the body's overall hormonal balance.

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 the TH-1 Hypothyroidism Panel May Be Ordered

The TH-1 Hypothyroidism panel is typically ordered when a patient presents symptoms suggestive of hypothyroidism or to monitor the effectiveness of ongoing thyroid treatment. Symptoms that may prompt ordering this panel include fatigue, weight gain, cold intolerance, dry skin, hair loss, and constipation. Additionally, it may be used in the evaluation of patients with known thyroid disorders to monitor their condition or the effectiveness of treatments.

What the TH-1 Hypothyroidism Panel Checks For

  • T3 Free (Free Triiodothyronine): This test measures the amount of T3 hormone not bound to proteins in the blood, offering insight into the metabolic activity driven by the thyroid. Free T3 levels can help in understanding how the body is using energy, with deviations from the norm indicating potential thyroid dysfunction.

  • T4 Free (Free Thyroxine): Free T4 measures the unbound thyroxine hormone in the bloodstream. It is essential for understanding the thyroid's capacity to produce and release the hormone, which is a precursor for T3 and crucial for metabolic processes.

  • Thyroid Stimulating Hormone (TSH): TSH is produced by the pituitary gland and regulates the production of thyroid hormones by stimulating the thyroid gland. Abnormal levels can indicate primary thyroid disease (when TSH is high and T4 is low) or a pituitary disorder (when TSH is low).

Getting a Deeper Understanding of Your Thyroid Health

While the TH-1 Hypothyroidism panel provides a solid foundation for initial thyroid function assessment, the TH-2, TH-3, and TH-4 panels offer a more comprehensive evaluation of thyroid health and its impact on overall metabolic function.

  • TH-2 Hypothyroidism Panel: This panel expands on the TH-1 by including a broad spectrum of tests such as a Complete Blood Count, Comprehensive Metabolic Panel, Hemoglobin A1c, and various vitamin and lipid assessments. It's particularly useful for patients with complex presentations where symptoms might not be solely attributable to thyroid dysfunction. The inclusion of lipid and vitamin levels, along with markers for diabetes and anemia, can provide insights into the broader metabolic impact of thyroid health.

  • TH-3 Hypothyroidism Panel: Building on the TH-2, the TH-3 panel adds thyroid antibody tests, which are crucial for diagnosing autoimmune thyroid diseases like Hashimoto's thyroiditis. The addition of Vitamin B6 further enhances the panel's capability to assess nutritional status and its potential impact on thyroid function and overall health.

  • TH-4 Hypothyroidism Panel: The most comprehensive, the TH-4 panel includes all the tests in the TH-3 and introduces TSH Receptor Binding Antibody and Thyroid Stimulating Immunoglobulin tests. These are particularly important for diagnosing and managing Graves' disease, an autoimmune disorder that can cause hyperthyroidism. This panel is best suited for patients with complex or unclear diagnoses, where multiple systems might be involved.

Conditions or Diseases the TH-1 Hypothyroidism Panel Can Check For

The TH-1 Hypothyroidism panel is primarily designed to detect various states of thyroid function, primarily hypothyroidism. Hypothyroidism, characterized by an underactive thyroid, can lead to a range of symptoms and is often linked to autoimmune thyroiditis (Hashimoto's disease). The panel helps in identifying overt hypothyroidism (elevated TSH and low T4) and subclinical hypothyroidism (elevated TSH with normal T4 levels). It can also be used in the context of hyperthyroidism to assess T3 and T4 levels.

Use of TH-1 Hypothyroidism Panel Results by Healthcare Professionals

Healthcare professionals use the results of the TH-1 Hypothyroidism panel to make informed decisions about diagnosis, treatment, and management of thyroid-related conditions. Elevated TSH and low T4/T3 levels typically indicate hypothyroidism, prompting further investigation or initiation of treatment such as thyroid hormone replacement. Conversely, low TSH with high T4/T3 levels may suggest hyperthyroidism, requiring a different treatment approach. These results can also help in adjusting medication dosages for patients already undergoing thyroid treatment.

The TH-1 Hypothyroidism panel serves as a critical tool in the initial evaluation and management of thyroid disorders, particularly hypothyroidism. By measuring key thyroid hormones and stimulating hormones, healthcare providers can gain valuable insights into a patient's thyroid function and overall metabolic health. While this panel offers a focused approach to thyroid assessment, more comprehensive panels like the TH-2, TH-3, and TH-4 provide deeper insights into the intricate interplay between the thyroid gland, metabolic health, and broader systemic functions, aiding in the holistic management of patients with complex or overlapping medical conditions.

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

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