MEDizzy - A 50-year-old female is evaluated for hypertension. Her

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Metabolic diseases

A 50-year-old female is evaluated for hypertension. Her blood pressure is 130/98. She complains of polyuria and mild muscle weakness. She is on no blood pressure medication. On physical examination, the PMI is displaced to the sixth intercostal space. There is no sign of congestive heart failure and no edema. Laboratory values are as follows: Na+: 147 mEq/dL K +: 2.3 mEq/dL Cl−: 112 mEq/dL HCO3: 27 mEq/dL The patient denies the use of diuretics or over-the-counter agents to decrease fluid retention or promote weight loss. She does not eat licorice. Which of the following tests is most useful in establishing a diagnosis?

ExplanationThe patient has diastolic hypertension with unprovoked hypokalemia. She is not taking diuretics. There is no edema on physical examination. Inappropriate aldosterone overproduction is a prime consideration in hypertension with hypokalemia. Hypersecretion of aldosterone increases distal tubular exchange of sodium for potassium with progressive depletion of body potassium. Hypertension is caused by increased sodium absorption. Interestingly, peripheral edema does not occur despite the sodium retention. Elevated aldosterone level and low plasma renin activity suggest the diagnosis of primary hyperaldosteronism. The plasma aldosterone to renin ratio is a useful screening test. A high ratio of > 30 strongly suggests aldosterone oversecretion. Lack of suppression of aldosterone (ie, autonomous overproduction), however, is necessary to definitively diagnose primary hyperaldosteronism. High aldosterone levels that are not suppressed by a 2 L saline load prove the diagnosis. CT scan of the adrenal glands is then ordered to distinguish an aldosterone-producing tumor from bilateral adrenal hyperplasia. Renin levels alone lack specificity. Suppressed renin activity occurs in about 25% of hypertensive patients with essential hypertension. Twenty-four-hour urine for free cortisol would be used in the workup of a patient with Cushing syndrome. Urinary metanephrine is a screening test for pheochromocytoma. Renal angiography is a test for renal artery stenosis.