MICROANATOMY

Detailed explanation-1: -At first, inorganic iodide is actively concentrated by thyroid follicular cells by the sodium iodide symporter. Low iodide levels stimulate the intake of iodide via increased expression of the sodium iodide symporter.

Detailed explanation-2: -NIS is an integral plasma membrane glycoprotein localized at the basolateral plasma membrane of thyrocytes (6). This protein plays an essential role in thyroid physiology by mediating uptake of iodide into the thyrocytes, a key step in thyroid hormone synthesis.

Detailed explanation-3: -There is a special pump on the basal membrane of the cells (faces the outside of the follicle) which line the thyroid follicles and transports iodide into the cell alongside sodium. There is another type of pump which transports sodium out of the cell, called the sodium-potassium pump.