Electrolyte Disorders USMLE Step 1 Practice Question
A 56-year-old man with a 10-year history of hypertension presents to clinic with a 3-month history of progressive muscle weakness, fatigue, and polyuria. He reports being on hydrochlorothiazide 25 mg daily for the past 5 years with suboptimal blood pressure control (current BP 168/102 mmHg). On examination, he appears fatigued but alert. Vital signs: HR 92/min, RR 16/min, BP 168/102 mmHg. Serum electrolytes reveal sodium 145 mEq/L, potassium 3.2 mEq/L, chloride 102 mEq/L, and HCO3- 28 mEq/L. Additional laboratory studies show serum creatinine 0.9 mg/dL, plasma aldosterone 28 ng/dL (normal <16), and plasma renin activity 0.3 ng/mL/hr (normal 0.5-2.5). Renal ultrasound shows normal-sized kidneys with no evidence of renal artery stenosis on duplex imaging. Which of the following is the most likely diagnosis?
Answer choices
- ASecondary hyperaldosteronism from renovascular hypertension
- BCushing syndrome
- CPrimary hyperaldosteronismCorrect answer
- DLicorice-induced hypokalemic hypertension
- EPheochromocytoma with secondary hypertension
- FMedication non-adherence with diuretic-induced hypokalemia
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