Which laboratory value would be most consistent with a diagnosis of adrenal insufficiency?

Which laboratory value would be most consistent with a diagnosis of adrenal insufficiency?

• A. Sodium 128 mEq/L
• B. Sodium 142 mEq/L
• C. Potassium 3.5 mEq/L
• D. Glucose 110 mg/dL

Answer: (A)

Adrenal insufficiency disrupts both aldosterone and cortisol. Low aldosterone leads the kidneys to waste sodium, and cortisol deficiency can raise ADH, promoting water retention and diluting serum sodium. A serum sodium of 128 mEq/L directly reflects this sodium-wasting and dilution effect, making hyponatremia the most characteristic finding in this condition. The other values don’t fit as well: a normal sodium value misses the sodium loss; a normal or low-normal potassium doesn’t show the anticipated aldosterone-driven potassium retention; and a glucose around 110 mg/dL is not a distinctive feature, since hypoglycemia is less reliably seen in adults with adrenal insufficiency except in crisis.

Adrenal insufficiency disrupts both aldosterone and cortisol. Low aldosterone leads the kidneys to waste sodium, and cortisol deficiency can raise ADH, promoting water retention and diluting serum sodium. A serum sodium of 128 mEq/L directly reflects this sodium-wasting and dilution effect, making hyponatremia the most characteristic finding in this condition.

The other values don’t fit as well: a normal sodium value misses the sodium loss; a normal or low-normal potassium doesn’t show the anticipated aldosterone-driven potassium retention; and a glucose around 110 mg/dL is not a distinctive feature, since hypoglycemia is less reliably seen in adults with adrenal insufficiency except in crisis.