Free Thyroxine

The primary thyroid hormone that the thyroid gland secretes into the bloodstream is called thyroxine (T4). In conjunction with triiodothyronine (T3), it is essential for controlling the body's metabolic rate, as well as growth, bone metabolism, cardiovascular health, and the proper development of the brain system and gonadal organs. In the bloodstream, T4 is a balanced combination of free and serum-bound hormone. The unbound, physiologically active version of T4 is called free T4 (fT4). One benefit of measuring free T4 is that it remains unaffected by variations in the quantities and characteristics of these binding proteins. In clinical routine diagnostics, free T4 is a helpful tool for determining the thyroid health. If thyroid issues are suspected, it should be examined along with TSH. It can also be used to track the effects of thyrosuppressive medication.