The Iodine is transported to the thyroid gland by:

(Active transport): Ref: 319-G, 314-SL (652- Ganong 23rd)* Iodine is transported actively from the blood in to the follicular cells against the electrochemical gradient (ACTIVE-TRANSPORT). This process by which the iodine is transported is called iodine trapping. A sodium- iodine symport pump called iodine pump transports iodine, along with sodium in to the follicular cells. From here, iodine is transported in to the follicular cavity by an iodide-cholride pump called pendrinPinocytosis - The substances with larger molecules cannot pass through the cell membrane either by active or by passive transport mechanism. Such substances are transported into the cell by a process called pinocytosis. The macromolecules like bacteria and antigens enter the cells by pinocytosis