This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Endocrinology, Subject name: Medicine
Hypomagnesemia is associated with which of the following- 
Select and explain. 
A. Alcoholism, B. Hypothyroidism, C. Both, D. None
A: Alcoholism
Answer: A: Alcoholism 
Explanation: A rising blood concentration of ethanol directly impairs tubular magnesium reabsorption, thus leading to hypomagnesemia. Hypehyroidism is a cause for hypomagnesemia and hypothyroidism causes hypermagnesemia. Reference : page 2462-63 Harrison's Principles of Internal Medicine 19th edition