Pituitary Disorders USMLE Step 1 Practice Question
A 35-year-old woman presents with polyuria (4 liters daily), polydipsia, and mild hypernatremia (Na+ 147 mEq/L). Serum osmolality is 305 mOsm/kg (elevated), and urine osmolality is 150 mOsm/kg (inappropriately low). After water deprivation testing, urine osmolality rises to 550 mOsm/kg. Subsequent desmopressin administration does not further increase urine osmolality. Which of the following is the most likely diagnosis?
Answer choices
- ASyndrome of inappropriate antidiuretic hormone secretion
- BCentral diabetes insipidus
- CNephrogenic diabetes insipidusCorrect answer
- DThyroid-stimulating hormone-secreting pituitary adenoma
- EPrimary polydipsia
- FAcute hyperglycemic hyperosmolar state
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