Which laboratory finding is typical in Cushing Syndrome?

In Cushing Syndrome, a hallmark laboratory finding is elevated levels of serum cortisol. This condition arises from excessive production of cortisol by the adrenal glands, which can be due to various causes such as adrenal adenomas, pituitary adenomas (Cushing disease), or ectopic ACTH production. The high serum cortisol levels reflect the overactivity of the hypothalamic-pituitary-adrenal (HPA) axis.

Measuring cortisol in the serum, especially at specific times of the day, can reveal diurnal variation that is often lost in individuals with Cushing Syndrome. Typically, serum cortisol is elevated in the early morning, and this pattern is altered in patients with Cushing's, as they may not exhibit the expected decline in cortisol levels throughout the day.

Low serum cortisol and low ACTH levels are not typical of Cushing Syndrome; in fact, low cortisol may suggest primary adrenal insufficiency or other conditions. High insulin levels are unrelated to the diagnosis of Cushing Syndrome and may be seen in other metabolic disorders but not specifically tied to cortisol dysregulation. Therefore, the identification of high serum cortisol as a typical finding in Cushing Syndrome is critical for diagnosing and managing this condition.