A 48-year-old woman presents for evaluation of difficult-to-control hypertension. She was diagnosed with hypertension 10 years ago and is currently taking lisinopril, amlodipine, hydrochlorothiazide, and metoprolol. Despite this four-drug regimen, her home blood pressure readings remain consistently in the 150s/90s. She reports intermittent muscle cramps and a sense of generalized fatigue over the last year but denies headaches, palpitations, or sweating. She does not consume black licorice. There is no family history of early-onset hypertension or stroke.