TPO g TPo g METABOLIC STEP INHIBITOR lumen卜 o、9DTH2O2Dr HO or T a lodide transport CIO, SCN- B lodination PTU MMI EOI C Coupling PTU MMI D Colloid resorption Colchicine, Li2+, Cytochalasin B E Proteolysis F Deiodination of DIT MIT Dinitrotyrosine G Deiodination of T4 PTU L og apical membran p cel AE MIT DIT. 5de- T4 T G ECF A basement membrane Mechanism of iodides