Comparison of 1 mg and 2 mg overnight dexamethasone suppression tests for the screening of Cushing's syndrome in obese patients.
OBJECTIVE
Obesity is currently a major public health problem and one of the potential underlying causes of obesity in a minority of patients is Cushing's syndrome (CS). Traditionally, the gold standard screening test for CS is 1 mg dexamethasone overnight suppression test. However, it is known that obese subjects have high false positive results with this test.


METHODS
We have therefore compared the 1 mg and 2 mg overnight dexamethasone suppression tests in obese subjects. Patients whose serum cortisol after ODST was >50 nM underwent and a low-dose dexamethasone suppression test (LDDST); 24-hour urine cortisol was collected for basal urinary free cortisol (UFC). For positive results after overnight 1-mg dexamethasone suppression test we also performed the overnight 2-mg dexamethasone suppression test.


METHODS
We prospectively evaluated 100 patients (22 men and 78 women, ranging in age from 17 to 73 years with a body mass index (BMI) >30 kg/m2 who had been referred to our hospital-affiliated endocrine clinic because of simple obesity. Suppression of serum cortisol to <50 nM (1.8 microg/dL) after dexamethasone administration was chosen as the cut-off point for normal suppression.


METHODS
Thyroid function tests, lipid profiles, homocysteine, antithyroglobulin, anti-thyroid peroxidase antibody levels, vitamin B12, folate levels, insulin resistance [by homeostasis model assessment (HOMA)] and 1.0 mg postdexamethasone (postdex) suppression cortisol levels were measured.


RESULTS
We found an 8% false-positive rate in 1 mg overnight test and 2% in 2 mg overnight test (p=0.001). There was no correlation between the cortisol levels after ODST and other parameters.


CONCLUSIONS
Our results indicate that the 2 mg overnight dexamethasone suppression test (ODST) is more convenient and accurate than 1-mg ODST as a screening test for excluding CS in subjects with simple obesity.
Sahin
Mustafa
M
Department of Endocrinology and Metabolism, Gulhane School of Medicine, Etlik, Ankara, Turkey. drsahinmustafa@yahoo.com
Kebapcilar
Levent
L
Taslipinar
Abdullah
A
Azal
Omer
O
Ozgurtas
Taner
T
Corakci
Ahmet
A
Akgul
Emin Ozgur
EO
Taslipinar
Mine Yavuz
MY
Yazici
Mahmut
M
Kutlu
Mustafa
M
D000293:Adolescent; D000328:Adult; D000368:Aged; D003480:Cushing Syndrome / Q000097:blood* / Q000150:complications / Q000175:diagnosis*; D003907:Dexamethasone / Q000008:administration & dosage*; D004305:Dose-Response Relationship, Drug; D005260:Female; D006801:Humans; D006854:Hydrocortisone / Q000097:blood; D008297:Male; D008875:Middle Aged; D009765:Obesity / Q000097:blood* / Q000150:complications / Q000175:diagnosis*; D011446:Prospective Studies; D013997:Time Factors; D055815:Young Adult
D003907:Dexamethasone; D006854:Hydrocortisone