A patient with central diabetes insipidus is started on desmopressin. After treatment, urine specific gravity rises from 1.002 to 1.015. What does this indicate?

Correct option is A

Desmopressin acts as synthetic ADH. A rise in urine specific gravity to 1.015 shows restored renal concentrating ability, confirming effective therapy in central DI.
Explanation of options: (a) ✔ Correct; increase in urine SG shows response. (b) ✘ Nephrogenic DI = no rise in SG. (c) ✘ Dose adjustment not needed; therapy working. (d) ✘ SIADH would cause excessively high SG, hyponatremia.