Iatrogenic Cushing Syndrome Workup

Updated: Oct 05, 2018
  • Author: Ha Cam Thuy Nguyen, MD; Chief Editor: Romesh Khardori, MD, PhD, FACP  more...
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Laboratory Studies

The diagnosis of Cushing syndrome requires demonstration of inappropriately high level of cortisol in the serum or urine. The levels should be measured when cortisol, according to its physiologic circadian rhythm, is supposed to be suppressed, meaning at midnight or when a patient is given exogenous glucocorticoids.

This concept gives rise to the following tests, which have been recommended as screening tests for Cushing syndrome: [26, 27]

  • Midnight serum or salivary cortisol [28, 29, 30]

  • 24-hour urine free cortisol

  • Low dose dexamethasone suppression test (Liddle test).

An ACTH level obtained at the same time with cortisol level can be helpful in identifying the etiology of Cushing syndrome.

Diagnosis of Cushing syndrome. Diagnosis of Cushing syndrome.