FT3, FT4, and RT3 Panel

There are no preparation instructions.

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: Reverse T3, Reverse Triiodothyronine, RT3, T3 Reverse RT3 LCMSMS, Triiodothyronine Reverse

T3 Reverse, LC/MS/MS

Reverse T3 produced in the thyroid comes from the conversion of the storage hormone T4. Your body, especially the liver, can constantly be converting T4 to RT3 as a way to get rid of any unneeded T4. In any given day approx. 40% of T4 goes to T3 and 20% of T4 goes to Reverse T3. However in any situation where your body needs to conserve energy and focus on something else, it will change the above percentages, changing the conversion of RT3 to 50% or more, and the T3 goes down, down. Examples are emotional, physical, or biological stress, such as being chronically or acutely sick (the flu, pneumonia, etc), after surgery, after a car accident or any acute injury, chronic stress causing high cortisol, being exposed to an extremely cold environment, diabetes, aging, or even being on drugs like beta blockers and amiodarone.

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.
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The FT3, FT4, and RT3 Panel panel contains 3 tests with 3 biomarkers.

Brief Description: The FT3, FT4, and RT3 Panel is a specialized set of thyroid function tests designed to provide a comprehensive assessment of an individual's thyroid health. This panel helps in diagnosing and monitoring thyroid disorders by measuring the levels of free T3, free T4, and reverse T3 in the blood. Each component of this panel plays a crucial role in understanding the complex hormonal feedback mechanisms and metabolic processes controlled by the thyroid gland.

Collection Method: Blood Draw

Specimen Type: Serum

Test Preparation: No preparation required

When and Why the FT3, FT4, and RT3 Panel May Be Ordered

This panel is typically ordered when symptoms suggest thyroid dysfunction, such as unexpected weight changes, mood disturbances, fatigue, or irregular heartbeats. It may also be requested to monitor the effectiveness of thyroid treatments, particularly in patients who are taking thyroid hormone replacements or have undergone thyroid surgery. The panel is critical for distinguishing between different types of thyroid disorders and ensuring that thyroid hormone levels are appropriately balanced in the body.

What the FT3, FT4, and RT3 Panel Checks For

This panel includes three essential thyroid tests:

  • T3 Free (FT3): Free T3 test measures the unbound Triiodothyronine hormone circulating in the bloodstream. FT3 is crucial for evaluating the metabolic activity and the actual bioavailable hormone that affects the body's processes.

  • T4 Free (FT4): Free T4 measures the unbound Thyroxine in the blood. This hormone is a precursor to T3 and is essential for understanding the overall function of the thyroid gland, including hormone production and regulation.

  • T3 Reverse (RT3): Reverse T3 is a metabolically inactive form of the hormone T3. This test helps assess how the body is metabolizing thyroid hormones, which is particularly useful in diagnosing thyroid-related metabolic imbalances.

Conditions and Diseases Detected by the FT3, FT4, and RT3 Panel

The FT3, FT4, and RT3 Panel is instrumental in diagnosing and managing several thyroid-related conditions:

  • Hyperthyroidism: Characterized by an overactive thyroid gland producing excessive amounts of thyroid hormones. Symptoms may include rapid heartbeat, weight loss, and anxiety. Elevated FT3 and FT4 levels typically indicate hyperthyroidism.

  • Hypothyroidism: In this condition, the thyroid gland does not produce enough hormones, leading to symptoms like fatigue, weight gain, and depression. Low FT3 and FT4 levels are indicative of hypothyroidism.

  • Euthyroid Sick Syndrome: Often seen in critically ill patients, this condition involves abnormal levels of FT3, FT4, and particularly high levels of RT3, without inherent thyroid gland dysfunction.

Using the Results of the FT3, FT4, and RT3 Panel

Healthcare professionals utilize the results from this panel to:

  • Diagnose Thyroid Disorders: The precise levels of FT3, FT4, and RT3 help differentiate between various thyroid conditions, providing a clear diagnosis.

  • Guide Treatment Decisions: Based on the results, treatments such as thyroid hormone replacement or adjustments in existing therapy can be made.

  • Monitor Treatment Efficacy: Regular testing with this panel helps track the success of treatment strategies, ensuring that thyroid hormone levels remain within the desired range.

The FT3, FT4, and RT3 Panel is a critical diagnostic resource in the field of endocrinology, providing detailed insights into the thyroid gland's function and its impact on metabolism. By measuring free and inactive forms of thyroid hormones, this panel helps in the accurate diagnosis, effective treatment, and diligent monitoring of thyroid-related health issues. Ultimately, it plays a pivotal role in enhancing patient outcomes and managing the complex symptoms associated with thyroid disorders.

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

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