WORKUP FOR MILD HYPERKALEMIA

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A 63-year-old asymptomatic man has had mild hyperkalemia (5.6-6.0 mEq/L) for the past six months. His physical examination and lab work are remarkable only for an elevated cholesterol level. He is a heavy smoker. Does this patient require workup for Addison’s disease? How would you proceed?
—Ashley Davis, MD, Boise, Idaho

Embedded within this complex question are two separate but potentially interrelated issues: persistent hyperkalemia and the specter of adrenal insufficiency. First, hyperkalemia is rare in normal subjects. Your history should include a thorough search for medication use, both OTC and prescription (e.g., nonsteroidal anti-inflammatory drugs and diuretics). A set of normal laboratory values in this case should, at a minimum, exclude renal dysfunction, diabetes, and metabolic acidosis.

In the absence of these abnormalities or rarer causes of hyperkalemia, such as selective defects in renal potassium handling and type I renal tubular acidosis, hypoaldosteronism should be considered. Hypoaldosteronism in the context of Addison’s disease results from primary failure of the adrenal glands. While we most often consider this diagnosis with more dramatic presentations of hypotension and/or shock (“adrenal crisis”), it is worth noting that early symptoms may be mild and include fatigue, weakness, anorexia, and weight loss.

Hyperkalemia is, in fact, relatively common, occurring in approximately 60% of cases of adrenal insufficiency. Even if your patient is presently asymptomatic, his condition may evolve over time. I would, therefore, proceed with testing of morning cortisol levels, followed by an adrenocorticotropic “stimulation” test if needed. Should you discover adrenal insufficiency in this patient, it would be important to rule out adrenal metastatic disease in the context of heavy tobacco use.
—Christopher Ruser, MD (101-4)

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