Free T3 and Free T4 Blood Test Panel

Free T3 and Free T4 Blood Test Panel

Quick Overview

Free Tri-iodothyronine (T3) Serum and Thyroxine (T4) Free Direct Serum.

Test #868

$60.00

Availability: In stock

Preparation No fasting required. Stop biotin consumption at least 72 hours prior to the collection.
Test Type Blood
Test Results 1-2 days. May take longer based on weather, holiday or lab delays.

Tri-iodothyronine (T3) normally represents only approximately 5% of the thyroid hormone and like thyroxine is almost entirely bound to the carrier proteins, with only 0.25% of the total being in the free state. Measurement of Free T-3 is of value in confirming the diagnosis of hyperthyroidism, when an elevated free or total thyroxine level is found. Abnormal total and free tri-iodothyronine concentrations can appear in T3 toxicosis, in the presence of normal thyroxine levels. Free T3 levels are not affected by carrier protein variation.

Free T4 is the active form of thyroxine and is thought to be a more accurate reflection of thyroid hormone function. The free T4 test is thought by many to be a more accurate reflection of thyroid hormone function and, in most cases, its use has replaced that of the total T4 test. A total T4 or free T4 test is primarily ordered in response to an abnormal TSH test result. Sometimes the T4 will be ordered along with a TSH to give the doctor a more complete evaluation of the adequacy of the thyroid hormone feedback system. These tests are usually ordered when a person has symptoms of hyperthroidism or hypothyroidism.

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