Dexamethasone Suppression-Crh Stimulation Test Provides Additional Case Detection in Patients Evaluated for Cushing Disease

Presentation Number: SAT-0644
Date of Presentation: June 21st, 2014

Ula Abed Alwahab, Georgiana Alina Dobri*, Charles Faiman, Laurence Kennedy and Amir Hekmat Hamrahian
Cleveland Clinic Foundation, Cleveland, OH


A serum cortisol level < 1.4 µg/dl after a 2 day low dose dexamethasone suppression test (LDDST) can be used to rule out Cushing disease. The diagnostic value of adding a corticotropin releasing hormone (CRH) stimulation test to the dexamethasone suppression test has been debated in the literature.
We reviewed the Cleveland Clinic pituitary database in order to identify patients who had a suppressed cortisol value (< 1.4 µg/dl) after a 2 day LDDST but had a cortisol value > 1.4 µg/dl at 15 min after CRH Stimulation(Dex-CRH test). Patients were instructed to take 8 doses of 0.5 mg of Dexamethasone every 6 hours orally starting at noon so the last dose of dexamethasone would be at 6 AM. Ovine CRH injection (1 µg/kg, maximum 100 µg) was given IV 2 hours afterwards.
A total of 154 patients underwent the Dex-CRH test between 2002 and 2013. Among them, we identified 4 patients (2.6%) [95% CI: 0.09%-5.11%] who were able to suppress cortisol adequately to <1.4 µg/dl after the 2 day LDDST but had an elevated cortisol of >1.4 µg/dl after CRH stimulation. The suppressed cortisol levels after LDDST were <0.1, <0.1, 1.1 and 1.2 µg/dl and the stimulated Cortisol levels after CRH injection were: 1.8, 2.1, 2.3 and 6.1 µg/dl.
The median (range) age was 36 years old(24-37). All were women.Three of these patients had pathology-proven new or recurrent Cushing disease; the fourth was lost to follow up. The dexamethasone levels prior to the administration of CRH were available in these 3 patients and they were: 493,496 and 496 ng/dl.
The addition of a CRH test after the 2 day LDDST confirmed the presence of Cushing disease in 3 out of 4 patients with an appropriately suppressed cortisol level after the 2 day LDDST. The standard LDDST is slightly different from the Dex-CRH test regarding the timing of dexamethasone administration. There are no data in the literature as to how this protocol variance would affect the results, however it is unlikely that the timing difference would matter since the biological plasma half-life of dexamethasone is reported as 36-54 hours.
The addition of the CRH test to the 2 day LDDST appears to provide additional case detection in a small percentage (up to 5%) of patients evaluated for new or recurrent Cushing disease.


Nothing to Disclose: UA, GAD, CF, LK, AHH