Overnight Dexamethasone Suppression Test: A Reliable Screen for Cushing's Syndrome in the Obese

Abstract

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 Ͻ80 nM (3 g/dL) was chosen as the cut-off point for normal suppression. Patients with serum cortisol levels Ն80 nM were evaluated for Cushing's syndrome. Results: Suppression of morning cortisol levels to Ͻ80 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. Discussion: 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.

Association of subclinical hypercortisolism with type 2 diabetes mellitus: a case-control study in hospitalized patients

“…1.8 mg/dl). In addition, regarding the control individuals, because they were matched with the diabetic patients, most of them were overweight/obese and hypertensive, two clinical conditions known to be associated with glucocorticoid excess; therefore, data obtained in our control group are not comparable with those obtained in the general population (3,24).…”

Comparison of 1 mg and 2 mg Overnight Dexamethasone Suppression Tests for the Screening of Cushing's Syndrome in Obese Patients

“…In a study by Ness-Abramof et al (5), an overnight dexamethasone suppression test was performed in 86 obese individuals. Seventy (12).…”

“…Low-dose dexamethasone suppression testing, especially the 1-mg overnight test, has been the mainstay of biochemical screening and is recommended in most standard texts (1). Obese individuals seem to show adequate suppression after the overnight dexamethasone (1 mg) suppression test; although studies have shown that there is a small percent of no suppressors (5). The methodology of cortisol assays has changed over time, with newer assays having higher specificity (1,6).…”

Perioperative Care of the Surgical Patient

“…Some clinical signs such as purplish striae, proximal muscle weakness, and osteopenia may be a clue for further work up. In a case with clinical features of Cushing's syndrome, the overnight dexamethasone suppression test is a choice for screening in the obese population since it gives fewer false positive rate than the 24 h free urinary cortisol test [14].…”