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MBBS QUESTION #10286
Question 1
A patient with polyuria and polydipsia fails to concentrate urine during a water deprivation test but responds appropriately (urine osmolality rises) after administration of exogenous desmopressin (an ADH analogue). This pattern is most consistent with:
  • Central (neurogenic) diabetes insipidus✔️
  • Nephrogenic diabetes insipidus
  • Primary polydipsia
  • Uncontrolled diabetes mellitus
Correct Answer Explanation
Central diabetes insipidus results from inadequate hypothalamic-pituitary ADH secretion; because the renal collecting duct receptors are intact, administering exogenous ADH (desmopressin) restores urine concentrating ability — in contrast to nephrogenic DI, where renal resistance to ADH means desmopressin produces little or no response.