Figure 1.

A – Comparison of chest X-rays at presentation with pre-treatment and last known normal chest X ray. All images were taken in postero-anterior orientation unless specified. (Left) At presentation, it revealed cardiomegaly without evidence of pleural effusion. Some soft tissue swelling is noticeable in the cervical region. (Middle) Chest X ray obtained prior to starting amiodarone reveals presence of cardiomegaly without the prominent neck soft tissue. (Right) Chest X ray taken four years previously reveals normal heart size and no soft tissue swelling. B – Mechanisms by which amiodarone inhibits thyroid function. Amiodarone inhibits (A) the peripheral conversion of T4 to T3 by inhibiting the enzyme 5'-deiodinase that converts T4 to T3 both within peripheral tissues and within the pituitary gland, (B) the entry of T4 into the peripheral tissues, and (C) the effect of T3 on thyroid-responsive tissues. T3 is the major negative regulator of TSH synthesis in the pituitary. The decrease in level of intra-pituitary T3 leads to increased synthesis of TSH seen in amiodarone-induced hypothyroidism