title: Limited Diagnostic Utility of Plasma Adrenocorticotropic Hormone for Differentiation between Adrenal Cushing Syndrome and Cushing Disease.
abstract: BACKGROUND
  Measurement of the plasma adrenocorticotropic hormone (ACTH) level has been recommended as the first diagnostic test for differentiating between ACTH-independent Cushing syndrome (CS) and ACTH-dependent CS. When plasma ACTH values are inconclusive, a differential diagnosis of CS can be made based upon measurement of the serum dehydroepiandrosterone sulfate (DHEA-S) level and results of the high-dose dexamethasone suppression test (HDST). The aim of this study was to assess the utility of plasma ACTH to differentiate adrenal CS from Cushing' disease (CD) and compare it with that of the HDST results and serum DHEA-S level.
  
  
  METHODS
  We performed a retrospective, multicenter study from January 2000 to May 2012 involving 92 patients with endogenous CS. The levels of plasma ACTH, serum cortisol, 24-hour urine free cortisol (UFC) after the HDST, and serum DHEA-S were measured.
  
  
  RESULTS
  Fifty-seven patients had adrenal CS and 35 patients had CD. The area under the curve of plasma ACTH, serum DHEA-S, percentage suppression of serum cortisol, and UFC after HDST were 0.954, 0.841, 0.950, and 0.997, respectively (all P<0.001). The cut-off values for plasma ACTH, percentage suppression of serum cortisol, and UFC after HDST were 5.3 pmol/L, 33.3%, and 61.6%, respectively. The sensitivity and specificity of plasma ACTH measurement were 84.2% and 94.3%, those of serum cortisol were 95.8% and 90.6%, and those of UFC after the HDST were 97.9% and 96.7%, respectively.
  
  
  CONCLUSIONS
  Significant overlap in plasma ACTH levels was seen between patients with adrenal CS and those with CD. The HDST may be useful in differentiating between these forms of the disease, especially when the plasma ACTH level alone is not conclusive.
authors.affiliation: Department of Internal Medicine, Seoul National University College of Medicine, Seoul, Korea.
authors.forename: A Ram
authors.initials: AR
authors.lastname: Hong
authors.affiliation: Department of Internal Medicine, Seoul National University College of Medicine, Seoul, Korea.
authors.forename: Jung Hee
authors.initials: JH
authors.lastname: Kim
authors.affiliation: Department of Internal Medicine, Seoul National University College of Medicine, Seoul, Korea.
authors.forename: Eun Shil
authors.initials: ES
authors.lastname: Hong
authors.affiliation: Department of Internal Medicine, Seoul National University College of Medicine, Seoul, Korea.
authors.forename: I Kyeong
authors.initials: IK
authors.lastname: Kim
authors.affiliation: Department of Internal Medicine, Seoul National University College of Medicine, Seoul, Korea.
authors.forename: Kyeong Seon
authors.initials: KS
authors.lastname: Park
authors.affiliation: Department of Internal Medicine, Seoul National University College of Medicine, Seoul, Korea.
authors.forename: Chang Ho
authors.initials: CH
authors.lastname: Ahn
authors.affiliation: Department of Internal Medicine, Seoul National University College of Medicine, Seoul, Korea.
authors.forename: Sang Wan
authors.initials: SW
authors.lastname: Kim
authors.affiliation: Department of Internal Medicine, Seoul National University College of Medicine, Seoul, Korea.
authors.forename: Chan Soo
authors.initials: CS
authors.lastname: Shin
authors.affiliation: Department of Internal Medicine, Seoul National University College of Medicine, Seoul, Korea. seongyk@plaza.snu.ac.kr.
authors.forename: Seong Yeon
authors.initials: SY
authors.lastname: Kim
keywords: Adrenal Cushing syndrome; Adrenocorticotropic hormone; Cushing disease; Dehydroepiandrosterone sulfate; High-dose dexamethasone suppression test