The Limited Value of Plasma Adrenocorticotrophic Hormone to Differentiate Adrenal Cushing's Syndrome from Cushing's Disease

Program: Abstracts - Orals, Featured Poster Presentations, and Posters
Session: SAT 26-40-Glucocorticoid Actions & Disease
Translational
Saturday, June 15, 2013: 1:45 PM-3:45 PM
Expo Halls ABC (Moscone Center)

Poster Board SAT-31
Ah Reum Khang*1, A Ram Hong1, Kyong Yeun Jung1, Jung Hee Kim2, Sang Wan Kim2 and Seong Yeon Kim2
1Seoul National University College of Medicine, 2Seoul National University College of Medicine, Seoul, South Korea
Measurement of plasma adrenocorticotrophic hormone (ACTH) is the first step to distinguish adrenal Cushing’s syndrome from Cushing’s disease according to the current guidelines. However, plasma ACTH levels were within normal range in about 30% of patients with adrenal Cushing’s syndrome due to the variability of ACTH assay. The high-dose dexamethasone suppression tests (HDST) and serum dehydroepiandrosterone sulfate (DHEA-S) had been used to make the differential diagnosis of Cushing’s syndrome. The aim of the present study was to assess the utility of plasma ACTH levels in differential diagnosis of Cushing’s syndrome and compare with HDST and serum DHEA-S.

We conducted a retrospective and multicenter study from January 2000 to May 2012. A total of 109 patients with endogenous Cushing’s syndrome were recruited. We excluded 17 patients with ectopic Cushing’s syndrome, recurrent Cushing’s syndrome, cyclic Cushing’s syndrome and subclinical Cushing’s syndrome. Serum cortisol or 24 hour urine free cortisol (UFC) after HDST (2mg per 6 hours for 2 days) and serum DHEA-S levels were measured.

Ninety-two patients were included in final analysis. Of them, 57 patients had adrenal Cushing’s syndrome and 35 patients had Cushing’s disease. Median age was 40 years in both groups. In receiver operating characteristic analysis, the area under the curve (AUC) of plasma ACTH, DHEA-S and percent suppression of serum cortisol or UFC after HDST were 0.954, 0.841, 0.950 and 0.997, repectively (all P <0.001). The cut-off value of plasma ACTH and percent suppression of serum cortisol or UFC after HDST was 24 pg/ml (normal range, 10 ~ 60 pg/ml), 33.3% and 61.6%. The sensitivity and specificity of plasma ACTH were 84.2%, 94.3%, and those of serum cortisol or UFC after HDST were 95.8%, 90.6% and 97.9%, 96.7%, respectively. Three patients with adrenal incidentalomas and non-suppressed plasma ACTH levels were successfully diagnosed with HDST.

In the present study, there was an overlap in plasma ACTH levels between patients with adrenal Cushing’s syndrome and those with Cushing’s disease. The high dose dexamethasone suppression test may be useful in etiological diagnosis of Cushing’s syndrome, especially when plasma ACTH levels alone were inconclusive.

Nothing to Disclose: ARK, ARH, KYJ, JHK, SWK, SYK

*Please take note of The Endocrine Society's News Embargo Policy at http://www.endo-society.org/endo2013/media.cfm