<unk> , or 3:5,3':5' tetra­iodothyronine (often abbreviated as<unk>  is the major hormone secreted by the follicular cells of the thyroid gland.<unk>  is transported in blood, with 99.95% of the secreted<unk>  being protein bound, principally to<unk>  ­binding globulin (TBG) and to a lesser extent to transthyretin and serum albumin.<unk>  is involved in controlling the rate of metabolic processes in the body and influencing physical development.
Note:<unk>  is a prohormone and a reservoir for the active thyroid hormone triiodothyronine (T3),<unk>  being converted as required in the tissues by deiodinases.
Type II deiodinase converts<unk>  into T3.
The "D" isomer is called "Dextrothyroxine" and is used as a lipid modifying agent.
The half life of<unk>  once released into the blood circulatory system is about 1 week
Thyroxine
Calcitriol 
Parathyroid hormone 
Cortisone
Levothyroxine 
Cholecalciferol
Doxercalciferol 
Vitamin D