The two main tests are the low-dose dexamethasone suppression
test (LDDST) and the ACTH stimulation test, but there are several other companion tests that may be recommended including the urine cortisohcreatinine ratio and advanced imaging such as abdominal ultrasound.
Based on clinical presentation the patient was tested for HAC by means of a low-dose dexamethasone suppression
Clinical burnout is not reflected in the cortisol awakening response, the day-curve or the response to a low-dose dexamethasone suppression
The cortisol levels could not be suppressed after both low-dose dexamethasone suppression
test and high-dose dexamethasone suppression test.
Overnight and Low-Dose Dexamethasone Suppression
Tests (ODST and LDDST).
The most common screening tests for suspected Cushing syndrome are the low-dose dexamethasone suppression
test and a 24-h urinary free cortisol (7).
The following tests can be used to make the diagnosis: 24-hour urinary free cortisol, low-dose dexamethasone suppression
, and late-night salivary cortisol.
Cortisol levels of the patient after both LDDST and HDDST, and percentage reduction of the cortisol levels, compared to baseline Test Cortisol levels after the test ([micro]g/dl) LDDST * 2.16 HDDST ** 3.98 Reduction of the cortisol levels: 82% * LDDST (Low-dose dexamethasone suppression
test): 48-hour, 2 mg/day DST ** HDDST (High-dose dexamethasone suppression test): 48-hour, 8 mg/day DST Table 3.
If Cushing's disease is suspected, obtain a 24-hour urinary free-cortisol excretion test or low-dose dexamethasone suppression
In a suspected case of adrenal neoplasm, or in elucidating the cause of secondary hypertension in addition to excluding pheochromocytoma by serum metanephrine or VMA in urine, cortisol production should also be measured by either serum cortisol levels or a low-dose dexamethasone suppression
The syndrome was defined as a plasma cortisol response greater than or equal to 1.8 mcg/dL to a low-dose dexamethasone suppression
Low-dose dexamethasone suppression
test (DST), 24-h urinary free cortisol (UFC) levels, highdose DST, corticotropin-releasing hormone (CRH) test and imaging modalities are among the current diagnostic approaches (4).