A67-year-old African-American woman was referred to a hypertension specialty clinic for refractory hypertension and intermittent hypokalemia. Evaluations for primary aldosteronism and renal artery stenosis were negative; plasma renin was low. She had been hypertensive for 15 years. Most recently, she had taken chlorthalidone 25 mg, amlodipine 5 mg, and metoprolol 50 mg twice daily. She was not ...