T3, Free

Description: A T3 Free test is a blood test that measures unbound triiodothyronine levels in your blood’s serum to evaluate your thyroid’s health and to screen for, diagnose, and monitor thyroid disorders such as hyperthyroidism.

Also Known As: Free T3 Test, Free Triiodothyronine Test, FT3 Test, T3F Test, Unbound T3 Test

Collection Method: Blood Draw

Specimen Type: Serum

Test Preparation: No preparation required

When is a T3 Free test ordered?

When a person's TSH test results are abnormal, a free T3 test may be recommended. When a person has symptoms that imply hyperthyroidism, it may be requested as part of the investigational workup, especially if the free T4 level is not elevated.

The following are possible signs and symptoms:

Free T3 may be ordered at regular intervals to monitor a known thyroid disease or to assess the efficacy of hyperthyroidism treatment.

What does a T3 Free 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 Free test:

Conditions where a T3 Free test is recommended:

How does my health care provider use a T3 Free test?

Thyroid function is measured with a free triiodothyronine test. It's usually ordered to assist identify hyperthyroidism, but it can also be used to track a person's therapy for a thyroid problem.

Thyroid hormones T3 and T4 are generated by the thyroid gland. They aid in the regulation of the rate at which the body expends energy and are governed by a feedback system. Thyroid-stimulating hormone boosts T4 and T3 synthesis and release. The liver and other tissues convert T4 into T3 as needed.

The majority of T4 and T3 in the blood is attached to protein, while just a small amount is free. Total T4, free T4, total T3, and free T3 can all be measured in blood tests.

Because the majority of T3 is coupled to protein, total T3 can be influenced by protein levels and binding ability, but free T3 is unaffected. Some professional standards, however, advocate total T3, thus either test can be used to evaluate thyroid function. To assist in diagnosing Graves disease, an autoimmune illness that is the most prevalent cause of hyperthyroidism, free T3 or total T3 may be ordered together with thyroid antibodies.

Following an abnormal TSH, a free T3 test is generally done, especially if the free T4 test is not high.

What does my T3 Free 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.

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