This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: ECG and Arrhythmia 3, Subject name: Medicine
[{'content': 'Which of the following is associated with A-V block? \nSelect and explain. \nA. Hypothyroidism, B. Hypehyroidism, C. Cushing disease, D. Pheochromocytoma', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Hypothyroidism will lead to myxedema which can interfere in A.V conduction pathway of hea. Etiologies of Atrioventricular Block Autonomic Carotid sinus hypersensitivity Vasovagal Metabolic/ Endocrine Hyperkalemia Hypermagnesemia Hypothyroidism Adrenal insufficiency Drug Related Beta blocker Calcium channel blockers Digitalis Adenosine Antiarrhythmics (class I and III) Lithium Infectious Endocarditis Lyme disease Chagas disese Syphilis Tuberculosis Diphtheria Toxoplasmosis Heritable/ congenital', 'role': 'assistant'}]