Review Question - QID 212548

A 54-year-old man comes to the emergency department for nausea and vomiting for the past 2 days. The patient reports that he felt tired and weak for the past week without any obvious precipitating factors. Past medical history is significant for hypertension controlled with hydrochlorothiazide. He denies diarrhea, changes in diet, recent surgery, vision changes, or skin pigmentation but endorses a 10-lb weight loss, headaches, fatigue, and a chronic cough for 2 years. He has smoked 2 packs per day for the past 20 years but denies alcohol use. Physical examination demonstrates generalized weakness with no peripheral edema. Laboratory tests are shown below:

Serum:
Na+: 120 mEq/L
Cl-: 97 mEq/L
K+: 3.4 mEq/L
HCO3-: 24 mEq/L
Ca2+: 10 mg/dL
Osmolality: 260 mOsm/L

Urine:
Na+: 25 mEq/L
Osmolality: 285 mOsm/L
Specific gravity: 1.200

What is the most likely finding in this patient?