Hypothyroidism has been reported as an uncommon- and possibly reversible - cause of atrioventricular (AV) node heart block. Common causes of AV block include ischemia; iatrogenic causes (typically medications, but also surgical complications), infiltrative conditions such as sarcoidosis, amyloidosis, or malignancy; and infectious conditions such as Lyme disease. This report describes a patient with complete heart block apparently...