Free Thyroxine T4

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free-t4
$56.23
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Overview

The thyroid gland produces and secretes T4, otherwise known as thyroxine. Proteins bind to T4 and carry it throughout the bloodstream. Once in the tissues, T4 is released from the proteins and is now free to convert into the more active form called T3. For this reason, many doctors believe that measuring free T4 is a more sensitive test for thyroid hormone production.

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 The thyroid gland produces and secretes T4, otherwise known as thyroxine. Proteins bind to T4 and carry it throughout the bloodstream. Once in the tissues, T4 is released from the proteins and is now free to convert into the more active form called T3. For this reason, many doctors believe that measuring free T4 is a more sensitive test for thyroid hormone production.

High levels of free T4 are associated with symptoms such as anxiety, insomnia, diarrhea, and muscle aches and pains. These symptoms collectively are known as hyperthyroidism.

Low levels of free T4, known as hypothyroidism, are associated with symptoms such as depression, weight gain, dry skin, hair loss, constipation, and cold intolerance.

The free T4 (FT4) assay measures the concentration of free thyroxine, the only biologically active fraction, in the serum (about 0.05% of the total T4). The free thyroxine is not affected by changes in concentrations of binding proteins such as TBG and thyroid-binding prealbumin. Thus such conditions as pregnancy, or estrogen and androgen therapy do not affect the FT4. Thus the FT4 assays generally are considered to provide a more reliable indication of true thyroid status because only the free hormone is physiologically active. In developing hypothyroidism, T4 (free T4) is the more sensitive indicator of developing the disease than is T3 (Free T3) and is therefore preferred for confirming hypothyroidism that has already been suggested by an elevated TSH result.

· Measurement of circulating thyroxine not bound to proteins (TBP)

· Reference Interval: 0.82−1.77 ng/dl (>19 yr old)

· Methodology: Electrochemiluminescence Immunoassay (ECLIA)

· The thyroid gland produces and secretes T4, otherwise known as thyroxine. Proteins bind to T4 and carry it throughout the bloodstream.

· Once in the tissues, T4 is released from the proteins and is now free to convert into the more active form called T3.

· Many physicians believe that measuring free T4 is a more sensitive test for thyroid hormone production


Fasting is not required. Take all medications as prescribed. Do not take supplements the day of the test. This test is also included in the Comprehensive Thyroid Profile.

NOTE: If you are taking biotin, please stop it 72 hours before the blood draw since it may interfere with hormone blood tests.

IMPORTANT:   We pride ourselves to have the best prices available in most U.S. states. However, due to local regulations we cannot serve customers in NY, NJ, MA, NH and RI.  No lab locations in HI and VT. 

 Please read the following frequently asked questions before placing an order: FAQs

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