To determine the mechanisms of manganese-induced hypothyroidism and understand how SLC30A10 and SLC39A14 cooperatively mediate manganese detoxification, here we produced <i>Slc39a14</i> single and <i>Slc30a10/Slc39a14</i> double knockout mice and compared their phenotypes with that of <i>Slc30a10</i> single knockouts.