After iatrogenic hypercortisolism due to exogenous glucocorticoid exposure is ruled out, there are 3 biochemical tests that can be used to test patients for endogenous hypercortisolism1
Tests for hypercortisolism
|1-mg overnight dexamethasone suppression test (DST)||Detects autonomous cortisol secretion in the blood2
|Late-night salivary cortisol (LNSC)||Measures the free cortisol in the saliva at the time point when cortisol should be at its lowest level1
||>ULN for the assay*|
|Urine free cortisol (UFC)||Measures excretion of circulating unbound cortisol in the urine over 24 hours2
||>ULN for the assay|
If tests are negative, retest in 6 months if signs and symptoms progress.1
Recommendations from screening guidelines:
“We suggest use of the 1-mg DST or late-night cortisol test, rather than UFC, in patients suspected of having mild Cushing syndrome.”—Endocrine Society1
“Given our objective of using tests with high sensitivity . . . we recommend use of the more stringent cutoff of 1.8 μg/dL.” —Endocrine Society1
“LNSC seems to be the best early predictor of recurrence of Cushing disease.”—AACE/ACE3
“Patients are screened for [mild Cushing syndrome] with a 1-mg overnight DST.”—AACE/AAES4
After an abnormal reading from initial tests and exclusion of other physiologic causes of excess cortisol (eg, pregnancy, obesity, diabetes), the Endocrine Society guidelines recommend the use of at least a second, different confirmatory test.1
AACE, American Association of Clinical Endocrinologists; AAES, American Association of Endocrine Surgeons; ACE, American College of Endocrinology; ULN, upper limit of normal.
*Abnormal range: >0.145 µg/dL (based on enzyme-linked immunosorbent assay and liquid chromatography with tandem mass spectrometry assay validation).