Description
Thyroxine (T4) is the most abundant thyroid hormone and plays an important role in the control of metabolism. The majority of circulating triiodothyronine (T3) results from the conversion of T4 in the peripheral tissues. In serum, T4 is bound to thyroxine-binding globulin (TBG), thyroxine-binding prealbumin (TBPA), and albumin. The serum-free T4 concentration is about 0.03% of the total T4 concentration.