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
Which of the following is associated with A-V block? 
Select and explain. 
A. Hypothyroidism, B. Hypehyroidism, C. Cushing disease, D. Pheochromocytoma
A: Hypothyroidism
Answer: A: Hypothyroidism 
Explanation: 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