In a patient suspected of having Cushing's syndrome, which laboratory finding would be expected?

In a patient suspected of having Cushing's syndrome, elevated serum cortisol levels are a hallmark finding. Cushing's syndrome results from excessive production of cortisol, which can occur due to various causes such as adrenal tumors, pituitary adenomas (Cushing's disease), or ectopic ACTH secretion. Measuring serum cortisol levels can help confirm the diagnosis of Cushing's syndrome.

High cortisol levels may lead to characteristic symptoms and signs associated with the syndrome, including weight gain, hypertension, glucose intolerance, and the classic "moon facies" appearance. In conjunction with other tests, such as 24-hour urinary free cortisol or late-night salivary cortisol levels, elevated serum cortisol is a critical indicator in diagnosing Cushing's syndrome.

The other potential findings associated with this condition, such as hyponatremia or hypoglycemia, are not typically present; in fact, patients with Cushing's syndrome often exhibit hyperglycemia due to cortisol's metabolic effects. Additionally, urine 17-ketosteroids would likely be increased rather than decreased, as they are byproducts of androgen metabolism which is often elevated in conditions of excess corticosteroids. Thus, elevated serum cortisol levels are consistent with the pathophysiology of Cushing's syndrome