Besides increased cortisol, which laboratory result would you expect in a patient with suspected Cushing disease?

Besides increased cortisol, which laboratory result would you expect in a patient with suspected Cushing disease?

• A. Serum sodium level of 155
• B. Serum potassium level of 4.5
• C. Serum calcium level of 9.0
• D. Blood glucose level of 70

Answer: (A)

Excess cortisol in Cushing disease acts like a mineralocorticoid on the kidney, promoting sodium reabsorption and potassium excretion in the distal tubules. This sodium retention expands circulating volume and raises serum sodium, while potassium is lost. Cortisol also drives gluconeogenesis and insulin resistance, so glucose is typically high. That’s why an elevated serum sodium fits best. The other options don’t align as closely: potassium would usually be low rather than normal, glucose would be elevated rather than 70, and calcium is typically normal in this context.

Excess cortisol in Cushing disease acts like a mineralocorticoid on the kidney, promoting sodium reabsorption and potassium excretion in the distal tubules. This sodium retention expands circulating volume and raises serum sodium, while potassium is lost. Cortisol also drives gluconeogenesis and insulin resistance, so glucose is typically high.

That’s why an elevated serum sodium fits best. The other options don’t align as closely: potassium would usually be low rather than normal, glucose would be elevated rather than 70, and calcium is typically normal in this context.