inhibits peroxidase enzyme which oxidizes iodide to iodine
adverse effects: serious liver injury and agranulocytosis (deficiency in neutrophils due to bone marrow damage, congestive heart failure, pulmonary edema
propylthiouracil also acts on peripheral tissue to inhibit monodeiodinase (catalyzes conversion of T4 to T3)
thiocyanate and perchlorate
competitive inhibitors of the sodium-iodide symport protein
block "iodide trapping" by follicular cells
used alone or in combination with other drugs that block thyroid hormone synthesis