This patient is a 34-year-old woman with a history of hypertension for 6 years who presents with recurrent muscle cramps, polyuria, and nocturia. She has persistent hypokalemia and her blood pressure is difficult to control despite multiple antihypertensive medications. Differential diagnoses include primary aldosteronism, renovascular disease, and Cushing's syndrome. Laboratory tests show elevated aldosterone and low renin levels, consistent with a diagnosis of primary aldosteronism or Conn's syndrome. Adrenal vein sampling is needed to determine if she has an aldosterone-producing adenoma or bilateral adrenal hyperplasia before deciding on treatment with adrenalectomy or medication.