This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Medicine
[{'content': 'The syndrome of inappropriate antidiuretic hormone is characterized by the following : \nSelect and explain. \nA. Hyponatremia and urine sodium excretion > 20 meq/l, B. Hypernatremia and urine sodium excretion > 20 meq/l, C. Hyponatremia and hyperkalemia, D. Hypernatremia and hypokalemia', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Answer is A (Hyponatremia and urine sodium excretion > 20 meq/l) : Cardinal features of SIADH include: Hyponatremia (dilutional hyponatremia with Na+ < 135 mmol/1) Decreased plasma osmolality (150 m osm). Urine sodium over 20 meq/1 Low Blood urea Nitrogen < 10 mg/L Hypouricemia ( Clinical Euvolemia - Absence of sign of hypervolemia (edema, ascitis) - Absence of signs of hypovolemia (ohostatic hypotension, tachycardia, features of dehydration) Absence of cardiac, liver or renal disease Normal thyroid and adrenal function A high BUN suggests a volume contracted state and excludes a diagnosis of SIADH. Q', 'role': 'assistant'}]