Synthesis of <a href="https://en.wikipedia.org/wiki/Thyroid_hormone" class="extiw" title="en:Thyroid hormone">thyroid hormones</a>.
<p>Reference:
</p>
<ul><li>Chapter 48, "SYNTHESIS OF THYROID HORMONES" in: <cite class="book" style="font-style:normal">Walter F., PhD. Boron (2003)      <i> Medical Physiology: A Cellular And Molecular Approach</i>, Elsevier/Saunders, pp. 1,300  <small><a href="https://en.wikipedia.org/wiki/International_Standard_Book_Number" class="extiw" title="en:International Standard Book Number">ISBN</a>:  <a href="//commons.wikimedia.org/wiki/Special:BookSources/1-4160-2328-3" title="Special:BookSources/1-4160-2328-3">1-4160-2328-3</a>. </small></cite></li></ul><h3><span class="mw-headline" id="Explanation">Explanation</span></h3>
<ul><li><a href="https://en.wikipedia.org/wiki/Thyroglobulin" class="extiw" title="en:Thyroglobulin">Thyroglobulin</a> is synthesized in the <a href="https://en.wikipedia.org/wiki/Rough_endoplasmic_reticulum" class="extiw" title="en:Rough endoplasmic reticulum">rough endoplasmic reticulum</a> and follows the <a href="https://en.wikipedia.org/wiki/Secretory_pathway" class="extiw" title="en:Secretory pathway">secretory pathway</a> to enter the colloid in the lumen of the <a href="https://en.wikipedia.org/wiki/thyroid_follicle" class="extiw" title="en:thyroid follicle">thyroid follicle</a> by <a href="https://en.wikipedia.org/wiki/exocytosis" class="extiw" title="en:exocytosis">exocytosis</a>.</li>
<li>Meanwhile, a <a href="https://en.wikipedia.org/wiki/sodium-iodide_symporter" class="extiw" title="en:sodium-iodide symporter">sodium-iodide (Na/I) symporter</a> pumps <a href="https://en.wikipedia.org/wiki/iodide" class="extiw" title="en:iodide">iodide</a> (I<sup>-</sup>) <a href="https://en.wikipedia.org/wiki/active_transport" class="extiw" title="en:active transport">actively</a> into the cell, which previously has crossed the <a href="https://en.wikipedia.org/wiki/endothelium" class="extiw" title="en:endothelium">endothelium</a> by largely unknown mechanisms.</li>
<li>This iodide enters the follicular lumen from the cytoplasm by the transporter <a href="https://en.wikipedia.org/wiki/pendrin" class="extiw" title="en:pendrin">pendrin</a>, in a purportedly <a href="https://en.wikipedia.org/wiki/passive_transport" class="extiw" title="en:passive transport">passive</a> manner.<sup id="cite_ref-1" class="reference"><a href="#cite_note-1">[1]</a></sup></li>
<li>In the colloid, iodide (I<sup>-</sup>) is <a href="https://en.wikipedia.org/wiki/Redox" class="extiw" title="en:Redox">oxidized</a> to iodine (I<sup>0</sup>) by an enzyme called <a href="https://en.wikipedia.org/wiki/Thyroid_peroxidase" class="extiw" title="en:Thyroid peroxidase">thyroid peroxidase</a>.</li>
<li>Iodine (I<sup>0</sup>) is very reactive and iodinates the thyroglobulin at <a href="https://en.wikipedia.org/wiki/Tyrosine" class="extiw" title="en:Tyrosine">tyrosyl</a> residues in its protein chain (in total containing approximately 120 tyrosyl residues).</li>
<li>In <i>conjugation</i>, adjacent tyrosyl residues are paired together.</li>
<li>The entire complex re-enters the follicular cell by <a href="https://en.wikipedia.org/wiki/endocytosis" class="extiw" title="en:endocytosis">endocytosis</a>.</li>
<li><a href="https://en.wikipedia.org/wiki/Proteolysis" class="extiw" title="en:Proteolysis">Proteolysis</a> by various <a href="https://en.wikipedia.org/wiki/protease" class="extiw" title="en:protease">proteases</a> liberates <a href="https://en.wikipedia.org/wiki/thyroxine" class="extiw" title="en:thyroxine">thyroxine</a> and <a href="https://en.wikipedia.org/wiki/triiodothyronine" class="extiw" title="en:triiodothyronine">triiodothyronine</a> molecules</li>
<li>Efflux of thyroxine and triiodothyronine from follicular cells, which appears to be largely through <a href="https://en.wikipedia.org/wiki/monocarboxylate_transporter_8" class="extiw" title="en:monocarboxylate transporter 8">monocarboxylate transporter (MCT) 8</a> and <a href="https://en.wikipedia.org/wiki/monocarboxylate_transporter_10" class="extiw" title="en:monocarboxylate transporter 10">10</a>,<sup id="cite_ref-FriesemaJansen2008_2-0" class="reference"><a href="#cite_note-FriesemaJansen2008-2">[2]</a></sup><sup id="cite_ref-BrixFührer2011_3-0" class="reference"><a href="#cite_note-BrixF%C3%BChrer2011-3">[3]</a></sup> and entry into the blood.</li></ul><h3><span class="mw-headline" id="Additional_references_for_details">Additional references for details</span></h3>
<div class="reflist" style="list-style-type: decimal;">
<ol class="references"><li id="cite_note-1"><span class="mw-cite-backlink"><a href="#cite_ref-1">↑</a></span> <span class="reference-text"><a rel="nofollow" class="external text" href="http://www.touchbriefings.com/pdf/2782/rousset.pdf">How Iodide Reaches its Site of Utilisation in the Thyroid Gland – Involvement of Solute Carrier 26A4 (Pendrin) and Solute Carrier 5A8 (Apical Iodide Transporter)</a> - a report by Bernard A Rousset. Touch Brieflings 2007</span>
</li>
<li id="cite_note-FriesemaJansen2008-2"><span class="mw-cite-backlink"><a href="#cite_ref-FriesemaJansen2008_2-0">↑</a></span> <span class="reference-text"><cite style="font-style:normal"> (2008). "Effective Cellular Uptake and Efflux of Thyroid Hormone by Human Monocarboxylate Transporter 10". <i>Molecular Endocrinology</i> <b>22</b> (6): 1357–1369. <a href="https://en.wikipedia.org/wiki/Digital_object_identifier" class="extiw" title="w:Digital object identifier">DOI</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1210/me.2007-0112">10.1210/me.2007-0112</a>. <a href="https://en.wikipedia.org/wiki/International_Standard_Serial_Number" class="extiw" title="en:International Standard Serial Number">ISSN</a> <a rel="nofollow" class="external text" href="https://www.worldcat.org/issn/0888-8809">0888-8809</a>.</cite></span>
</li>
<li id="cite_note-BrixFührer2011-3"><span class="mw-cite-backlink"><a href="#cite_ref-BrixF%C3%BChrer2011_3-0">↑</a></span> <span class="reference-text"><cite style="font-style:normal"> (2011). "Molecules important for thyroid hormone synthesis and action - known facts and future perspectives". <i>Thyroid Research</i> <b>4</b> (Suppl 1): S9. <a href="https://en.wikipedia.org/wiki/Digital_object_identifier" class="extiw" title="w:Digital object identifier">DOI</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1186/1756-6614-4-S1-S9">10.1186/1756-6614-4-S1-S9</a>. <a href="https://en.wikipedia.org/wiki/International_Standard_Serial_Number" class="extiw" title="en:International Standard Serial Number">ISSN</a> <a rel="nofollow" class="external text" href="https://www.worldcat.org/issn/1756-6614">1756-6614</a>.</cite></span>
</li>
</ol></div>
<a href="//commons.wikimedia.org/wiki/User:Mikael_H%C3%A4ggstr%C3%B6m" title="User:Mikael Häggström">Mikael Häggström</a>
2011-06-16
<p>Mainly <span class="int-own-work" lang="en">Own work</span>
</p>
<ul><li>Source image for nucleus derivative:</li></ul><ul class="gallery mw-gallery-traditional"><li class="gallerybox" style="width: 155px"><div style="width: 155px">
			<div class="thumb" style="width: 150px;"><div style="margin:31px auto;"><a href="//commons.wikimedia.org/wiki/File:Plant_cell_structure-en.svg" class="image" title="(Public Domain license)"><img alt="(Public Domain license)" src="https://upload.wikimedia.org/wikipedia/commons/thumb/d/d8/Plant_cell_structure-en.svg/120px-Plant_cell_structure-en.svg.png" decoding="async" width="120" height="88" srcset="https://upload.wikimedia.org/wikipedia/commons/thumb/d/d8/Plant_cell_structure-en.svg/180px-Plant_cell_structure-en.svg.png 1.5x, https://upload.wikimedia.org/wikipedia/commons/thumb/d/d8/Plant_cell_structure-en.svg/240px-Plant_cell_structure-en.svg.png 2x" data-file-width="649" data-file-height="475"></a></div></div>
			<div class="gallerytext">
<p>(Public Domain license)
</p>
			</div>
		</div></li>
</ul>