USMLE Step 1 – Question of the Week #2

A 38-year-old man presents to physician with complains of excessive thirst and excessive passage of urine for last one week. He also mentions that he has to get up at night for urination, which was not a problem a few days before. He is an otherwise healthy man with no known medical condition. Physical examination of the man is normal. Important findings in laboratory evaluation are as follows:

Urine osmolality          175 mOsmol/kg H2O

Urine specific gravity  1.002

Serum osmolality        290 mOsmol/kg H2O

The man was advised to undergo water deprivation test, which confirmed that urine osmolality remained less than 300 mOsmol/kg H2O and it did not improve after administration of antidiuretic hormone.  After appropriate laboratory evaluation, the physician confirms that the man’s condition is due to an electrolyte abnormality. Which of the following electrolyte abnormalities is known to cause the condition the man is suffering from? Access full Qbank at – 30 day free trial. 

A. Hypokalemia

B. Hypochloremia

C. Hypocalcemia

D. Hypomagnesemia

E. Hyponatremia