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': 'Choose the best Lab value for a patient with central diabetes insipidus \nSelect and explain. \nA. Urinary Osmolality - 50, Serum Osmolality - 300, B. Urinary Osmolality - 500, Serum Osmolality - 260, C. Urinary Osmolality - 50, Serum Osmolality - 260, D. Urinary Osmolality - 500, Serum Osmolality - 100', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Diabetes insipidus is the reverse of SIADH, here the ADH level is decreased which leads to excessive water loss from the kidney resulting in hypertonic plasma associated with dilute urine.\nIt can be\n\n- Central\xa0 \xa0\xa0 →\xa0(due to impaired secretion of ADH from the neurohypophysis)\n- Nephrogenic\xa0→ \xa0\xa0(due to renal insensitivity or nonresponsiveness to ADH).\n\nIn both circumstances. the serum osnzolality is increased with inappropriately low urine osmolalitv.\nThe two may be distinguished, however, by the response to either exogenous or endogenous vasopressin.\nIn neurogenic (central) DI,\n\n- ADH levels are 100, and the kidney rapidly acts to conserve water once exogenous ADH is administered.\n\nIn contrast, in nephrogenic DI,\n\n- ADH is associated with normal or increased ADHe levels and administration of additional ADH has no\xa0significant effect on renal water reabsorption.\nAlso known', 'role': 'assistant'}]