Dexamethasone-suppressed corticotropin-releasing hormone stimulation test in morbid obese adults

Purpose In order to differentiate between Cushing's syndrome (CS) and Pseudo-Cushing's syndrome, it is customary to use a test that is conducted by cortisol suppression with low-dose dexamethasone, followed by the administration of corticotropin releasing hormone (Dex-CRH test). In children with severe obesity, Dex-CRH test has shown a specificity of 55%. The aim of current study was to evaluate the specificity of Dex-CRH test in morbid obese adults. Methods The study included a total of 19 subjects with a body mass index (BMI) equal or higher than 40 kg/m². In all subjects Dex-CRH test was performed, and 24 h urinary free cortisol was collected prior the test and during the second day of dexamethasone administration (2nd-day-UFC). Results BMI was 45.1 ± 4.6 kg/m² and 45.7 ± 3.3 kg/m² in women and men, respectively. 14 subjects underwent bariatric surgery. No subject had surgical or perioperative complications and surgically treated subjects had mean body weight loss of 46.5 ± 16.6 kg. All except for 2 subjects had normal Dex-CRH test, as 15-min cortisol falling below 1.4 μg/dl. During follow-up, no subject gained additional weight, neither developed signs of CS. 15-min-cortisol concentration of 1.4 μg/dl revealed a specificity of 89% and 2nd-day-UFC of 16 μg/24 h showed a specificity of 100%. Conclusions Morbid obesity in adults seems not to comprise a significant confounder in Dex-CRH test, and 15-min-cortisol concentration of 1.4 μg/dl had a higher specificity than previously reported in obese children.