A 22 year-old man presents to the clinic due to excessive urination. He goes to the restroom almost every 15 minutes. His physical examination is otherwise normal. Laboratory tests show Serum Na: 140 mEq/L Urine output: 4 L/24 hours Urine is negative for glucose and protein and no pus cells Urine Na: 18 mEq/L Urine osmolality: 260 mOsm/kg after 4h fluid deprivation. What is the most likely diagnosis? A-Diabetes mellitus B-Diabetes insipidus C-Psychogenic polydipsia D-Urinary tract infection E-Solute diuresis Answer
