24 h-kinetics of iodide uptake in amiodarone induced hypothyroidism

Amiodarone induced hypothyroidism (AIH) is assumed to result from a failure of the thyroid to escape from the inhibitory effect of inorganic iodine on its organification as a consequence of uninhibited iodide trapping. This hypothesis was supported by the 24h kinetics of radioiodine uptake in a patient with AIH. 131I uptake reached a maximum after 2h and remained unchanged from 2h to 24h. 131I uptake was in the normal range from 1 1/2h to 7h and clearly subnormal after 9h. The normal early 131I uptake was due to the non inhibition of the iodide-concentrating mechanism and the low 24h radioactivity to the decreased iodide organification. These findings presumably explain the mechanism of AIH.