K+: 3.0 mmol/L; GLU: 9.3 mmol/L; CORT (AM): 990 nmol/L. What is the likely diagnosis?

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Multiple Choice

K+: 3.0 mmol/L; GLU: 9.3 mmol/L; CORT (AM): 990 nmol/L. What is the likely diagnosis?

Excess cortisol drives this pattern. Very high morning cortisol indicates hypercortisolism, and that excess cortisol raises blood glucose through increased gluconeogenesis and insulin resistance, so hyperglycemia is expected. At high levels, cortisol also acts like a mineralocorticoid in the kidneys, promoting potassium loss and resulting in low potassium. That combination—high glucose plus low potassium with elevated cortisol—is characteristic of Cushing's syndrome. Addison's would show low cortisol and often high potassium, not this profile; diabetes alone explains hyperglycemia but not the accompanying low potassium or the cortisol elevation; thyroid storm involves different hormonal disturbances and wouldn’t produce this cortisol and electrolyte pattern.

Excess cortisol drives this pattern. Very high morning cortisol indicates hypercortisolism, and that excess cortisol raises blood glucose through increased gluconeogenesis and insulin resistance, so hyperglycemia is expected. At high levels, cortisol also acts like a mineralocorticoid in the kidneys, promoting potassium loss and resulting in low potassium. That combination—high glucose plus low potassium with elevated cortisol—is characteristic of Cushing's syndrome. Addison's would show low cortisol and often high potassium, not this profile; diabetes alone explains hyperglycemia but not the accompanying low potassium or the cortisol elevation; thyroid storm involves different hormonal disturbances and wouldn’t produce this cortisol and electrolyte pattern.

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