<prompt> Antiarrythmic drug causing hypothyroidism?AmiodaroneAmrinoneDigoxinProcainamide  <response>: 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 hypothyroidismEscape from Wolff-Chaikoff effectInhibition of deiodinase activity. Conversion of T4-T,3Enhanced T4, rT3 levelsDecreased T3 levelsElevated TSH levels TSH normal after 1-3 monthsAmiodarone induced hyperthyroidism - CausesJod - Basedow effectThyroiditis like conditionsAutoimmune Graves diseaseOther important side effects of amiodaroneMnemonic: The Periphery of My Left Cornea is Photosensitive To BlueThyroid dysfunctionPeripheral neuropathyMyocardial depressionLung fibrosisComeal depositsPhotosensitivityTorsades de pointesBlue pigmentation 