Inhibition
Some anions like perchlorate, pertechnetate and thiocyanate, can affect iodide capture by competitive inhibition because they can use the symporter when their concentration in plasma is high, even though they have less affinity for NIS than iodide has. Many plant cyanogenic glycosides, which are important pesticides, also act via inhibition of NIS in a large part of animal cells of herbivores and parasites and not in plant cells.
Read more about this topic: Sodium-iodide Symporter