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': 'Syndrome of inappropriate antidiuretic hormone secretion is diagnosed by all EXCEPT: \nSelect and explain. \nA. Hyponatremia, B. Decreased osmolality (< 280 mosm/kg), C. Normal blood nitrogen, D. Normal thyroid function', 'role': 'user'}, {'content': 'Answer: C \nExplanation: [Cl (Normal blood urea nitrogen) (2102-H 16lh) (769-70-CMDT-2009) (277-78-H17th)* Syndrome of inappropriate antidiuretic hormone secretion (SIADH)Clinical features* Hyponatremia* Decreased osmolality (< 280 mosm/kg) with inappropriately increased urine osmolalilty (> 150 mosm/kg)* Absence of cardiac, renal or liver disease* Normal thyroid and adrenal function* Urine sodium usually over 20 mEq/L.Other changes* Low blood urea nitrogen (BUN) (< 10 mg/dL)* Hypouricemia (< 4 mg/dL)* A high BUN suggests a volume state, which excludes a diagnosis of SIADH.', 'role': 'assistant'}]