Product Code Database
Example Keywords: office -the $76
barcode-scavenger
   » » Wiki: Thyroxine
Tag Wiki 'Thyroxine'.
Tag

Thyroxine, also known as T4, is a produced by the . It is the primary form of found in the blood and acts as a of the more active thyroid hormone, (T3). Thyroxine and its active metabolites are essential for regulating , supporting heart and muscle function, promoting brain development, and maintaining .


Regulation
Thyroxine has a of approximately one week and hence maintains relatively stable blood levels. Its production and release are controlled through a complex feedback loop involving the , , and thyroid gland. This regulatory system ensures that optimal hormone levels are maintained.


Biosynthesis
Thyroxine biosynthesis is a multi-step process that occurs in follicular cell within the thyroid gland. The synthesis of thyroxine requires adequate supply and appropriate hormonal control.

The process begins with the active uptake of iodide from the bloodstream by thyroid follicular cells through the sodium/iodide symporter (NIS) located in the basolateral membrane. Once inside the cell, iodide is transported to the follicular lumen, where it undergoes oxidation by the enzyme thyroid peroxidase (TPO) in the presence of hydrogen peroxide generated by the oxidase DUOX2. The oxidized iodine then iodinates tyrosyl residues of (Tg), a synthesized by thyroid cells and stored in the follicular lumen. This process, known as , results in the formation of (MIT) and (DIT) residues within the Tg molecule.

The final step in thyroxine synthesis involves the mediated coupling of two DIT residues, catalyzed by TPO, to form T4 while still attached to the Tg backbone. When thyroid hormone is needed, Tg is internalized by thyrocytes, and proteolytic enzymes in lysosomes cleave the T4 from Tg, allowing for its release into the bloodstream. This intricate biosynthetic pathway is tightly regulated by thyroid-stimulating hormone (TSH) from the pituitary gland, which influences virtually every stage of thyroid hormone production.

Page 1 of 1
1
Page 1 of 1
1

Account

Social:
Pages:  ..   .. 
Items:  .. 

Navigation

General: Atom Feed Atom Feed  .. 
Help:  ..   .. 
Category:  ..   .. 
Media:  ..   .. 
Posts:  ..   ..   .. 

Statistics

Page:  .. 
Summary:  .. 
1 Tags
10/10 Page Rank
5 Page Refs
1s Time