Chemistry of thyroid hormones doesn't make sense

[scilearner]

Hello everyone,

 

This is a DIT molecule.

 

http://www.ebi.ac.uk/chebi/displayImage.do?defaultImage=true&imageIndex=0&chebiId=15768

 

Now the book says there is a coupling reaction DIT + DIT ----> gives T4 molecule or tyroxine hormone

 

Now this is how T4 looks like

 

http://www.speciation.net/Public/Data/sp/Image/thyroxine.gif

 

I don't understand how you can get this when there is a addition reaction between these two. Does coupling mean something else. Thank you

 

I don't know why but it says pictures are not allowed in this board.