GENERAL HISTOLOGY

Detailed explanation-1: -Uptake of iodide into the thyrocytes is mediated by an intrinsic membrane glycoprotein, the sodium-iodide symporter (NIS), which actively cotransports two sodium cations per each iodide anion. NIS-mediated transport of iodide is driven by the electrochemical sodium gradient generated by the Na+/K+-ATPase.

Detailed explanation-2: -Iodide transport in thyroid cells As illustrated in Figure 1, the NIS (SLC5A5), a member of the solute carrier family 5, located at the basolateral plasma membrane of the thyroid follicular cells actively transports iodide into the thyroid using the electrochemical gradient generated by the Na, K-ATPase [9-11].

Detailed explanation-3: -Within the thyroid, iodide is moved to the colloid space via pendrin, a sodium-independent iodide/chloride transport protein. The thyroperoxidase (TPO) enzyme then organifies iodide by binding it to tyrosine residues on thyroglobulin forming monoiodotyrosine (MIT) or diiodotyrosine (DIT).

Detailed explanation-4: -The sodium/iodide symporter (NIS) is an intrinsic plasma membrane protein that mediates active iodide transport into the thyroid gland and into several extrathyroidal tissues. NIS-mediated iodide uptake plays a pivotal role in the biosynthesis of thyroid hormones, of which iodide is an essential constituent.