Q: Amiodarone causes thyroid problems because?
A) It resembles thyroxine
B) It contains high amount of Iodine
C) Both A and B
D) It blocks potassium channels
E) It is idiopathic (cause unknown)
Amiodarone chemically resembles thyroxine, and it binds to the nuclear thyroid receptor which contributes to its toxic effect on thyroid, either amiodarone-induced thyrotoxicosis (AIT) or amiodarone-induced hypothyroidism (AIH). Also, iodine in Amiodarone play significant role in pathology.
There are two main forms of AIT: type 1, a form of iodine-induced hyperthyroidism, and type 2, a drug-induced destructive thyroiditis. However, mixed/indefinite forms also exists.
The most likely mechanism of AIH is an enhanced susceptibility to the inhibitory effect of iodine on thyroid hormone synthesis