title: Overnight dexamethasone suppression test: a reliable screen for Cushing's syndrome in the obese.
abstract: OBJECTIVE
  Reevaluation of the validity of the 1-mg overnight dexamethasone suppression test (ODST) as a screening test for Cushing's syndrome in obese patients.
  
  
  METHODS
  Eighty-six obese patients (body mass index, 30 to 53 kg/m(2)) that were referred to a general endocrine outpatient clinic for evaluation of simple obesity, diabetes mellitus, hypertension, polycystic ovary disease, or pituitary tumor. One milligram dexamethasone was administered orally at 11:00 PM, and serum cortisol levels were measured the following morning between 8:00 AM and 9:00 AM. Suppression of serum cortisol to <80 nM (3 micro g/dL) was chosen as the cut-off point for normal suppression. Patients with serum cortisol levels > or =80 nM were evaluated for Cushing's syndrome.
  
  
  RESULTS
  Suppression of morning cortisol levels to <80 nM occurred in 79 of the 86 obese patients. Seven patients had serum cortisol levels higher than 80 nM; five were eventually diagnosed with Cushing's syndrome and two were considered false positive results in view of normal 24-hour free urinary cortisol and normal suppression on a low dose dexamethasone suppression test (0.5 mg of dexamethasone every 6 hours for 2 days). We found a false positive rate of 2.3% for the ODST using a cut-off serum cortisol of 80 nM.
  
  
  CONCLUSIONS
  The ODST is a valid screening test for Cushing's syndrome in the obese population. The false positive rate was 2.3%, even when using a strict cut-off serum cortisol of 80 nM. Abnormal cortisol suppression in obese patients should be investigated and not be considered false positive results.
authors.affiliation: Section of Endocrinology, Diabetes, and Nutrition, Boston Medical Center and Boston University School of Medicine, Massachusetts 02118, USA. rosane.abramofness@bmc.org
authors.forename: Rosane
authors.initials: R
authors.lastname: Ness-Abramof
authors.forename: Dan
authors.initials: D
authors.lastname: Nabriski
authors.forename: Caroline M
authors.initials: CM
authors.lastname: Apovian
authors.forename: Mark
authors.initials: M
authors.lastname: Niven
authors.forename: Eliahu
authors.initials: E
authors.lastname: Weiss
authors.forename: Menachem S
authors.initials: MS
authors.lastname: Shapiro
authors.forename: Louis
authors.initials: L
authors.lastname: Shenkman
mesh_terms: D000328:Adult; D015992:Body Mass Index; D003480:Cushing Syndrome / Q000150:complications / Q000175:diagnosis*; D003907:Dexamethasone; D005189:False Positive Reactions; D005260:Female; D005938:Glucocorticoids; D006801:Humans; D006854:Hydrocortisone / Q000097:blood; D008297:Male; D008875:Middle Aged; D009765:Obesity / Q000150:complications*
chemical_list: D005938:Glucocorticoids; D003907:Dexamethasone; D006854:Hydrocortisone