Overnight (1 mg) dexamethasone suppression testing reliably distinguishes non-cushingoid obesity from Cushing's syndrome.
To determine the sensitivity of the overnight 1-mg dexamethasone suppression test in diagnosing Cushing's syndrome, we evaluated the cortisol responses of 55 subjects (25 non-obese individuals with body mass index less than 25 kg/m2, 20 obese individuals with body mass index greater than 30 kg/m2, and 10 patients with surgically proven Cushing's syndrome) following ingestion of 1 mg dexamethasone at midnight. The basal 8 AM plasma cortisol levels among non-obese and obese individuals and patients with Cushing's syndrome were 310 +/- 85, 377 +/- 91, and 813 +/- 270 nmol/L, respectively. Following 1 mg of dexamethasone, Cushing's syndrome patients showed minimal suppression of cortisol to 609 +/- 180 nmol/L (P = 0.79). Non-obese and obese individuals suppressed to 18.7 +/- 6.0 nmol/L (P less than 0.001) and 22 +/- 7.1 nmol/L (P = 0.003), respectively. The results demonstrated similar cortisol responses to overnight dexamethasone suppression in obese and non-obese groups, and clearly distinguished these subjects from those with Cushing's syndrome. Obesity is not a confounding factor in the 1-mg dexamethasone suppression test.
Fok
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AC
Department of Medicine I (Endocrinology), Singapore, General Hospital.
Tan
K T
KT
Jacob
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Sum
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CF
D000328:Adult; D003480:Cushing Syndrome / Q000175:diagnosis*; D003907:Dexamethasone / Q000008:administration & dosage*; D003937:Diagnosis, Differential; D005260:Female; D006801:Humans; D008297:Male; D009765:Obesity / Q000175:diagnosis*; D012680:Sensitivity and Specificity; D013997:Time Factors
D003907:Dexamethasone