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
[{'content': 'Tolvaptan is approved for use in - \nSelect and explain. \nA. High Na, B. High K, C. High Cu, D. Low Na', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Tolvaptan is an aquaretic drug that functions as a selective, competitive vasopressin receptor 2 antagonist used to treat hyponatremia associated with congestive hea failure, cirrhosis, and the syndrome of inappropriate antidiuretic hormone . This medication is used to treat low levels of salt (sodium) in the blood, which can result from conditions such as hea failure and ceain hormone imbalances . Tolvaptan improves urine flow without causing the body to lose too much sodium as you urinate. Ref - pubmed.com', 'role': 'assistant'}]