Antiarrythmic drug causing hypothyroidism?

Ans: a (Amiodarone) Ref: Harrison, 16th ed, p. 2119; 17th ed, p. 2230Amiodarone is a class III anti arrhythmic, structurally related to thyroid hormones and contains high amounts of I2 (39% by weight). It leads to >40 fold increase in plasma and urine I2, levels.Amiodarone induces hypothyroidism by following mechanisms:Inhibit deiodinase activityWolff-chaikoff effect (Iodine induced suppression of thyroid iodination and organification.Metabolites have weak antagonistic action of thyroid hormoneEffects of amiodarone on thyroid functionInitiation of treatmentInhibitory effects of iodine on T4 releaseWolff-Chaikoff effectDecrease in transient T4 level (hypothyroidism)||Escape from Wolff-Chaikoff effectInhibition of deiodinase activity. (Conversion of 'T4-T,3)Enhanced T4, rT3 levelsDecreased T3 levelsElevated TSH levels (TSH normal after 1-3 months)Amiodarone induced hyperthyroidism - CausesJod - Basedow effectThyroiditis like conditionsAutoimmune Grave's diseaseOther important side effects of amiodaroneMnemonic: The Periphery of My Left Cornea is Photosensitive To BlueThyroid dysfunctionPeripheral neuropathyMyocardial depressionLung fibrosisComeal depositsPhotosensitivityTorsades de pointesBlue pigmentation