Endocrine Abstracts (2012) 28 P227

Evaluation of overnight dexamethasone suppression test in obese individuals

Kashif Hafeez & Layla Meshykhi


EastBourne Endocrine Department, 1, Eastbourne, United Kingdom.


Introduction: Obesity is becoming a major health concern and it is one of the common referrals seen in the Endocrine clinics for evaluation and further management. Cushing’s syndrome is one of the rare causes of Obesity particularly central but may be general.Overnight Dexamethasone suppression test(ODST)is used as screening test for Cushing’s Syndrome.Suppression of Cortisol to 80 nmol/l after ODST is expected in most of the normal individuals,one of the difficulties is false positive result in obese individual in 13% to 53% cases. Aim: Evaluation of the of the 1 mg overnight Dexamethasone suppression test (ODST) as a screening test for Cushing’s syndrome in Obese patients Methods:Retrospective study over the period of one year. 50 Obese patients (BMI 30 to 61 kgm/m2)were included who were referred to a general endocrine outpatient clinic for evaluation of simple Obesity, Diabetes Mellitus, Hypertension, Polycystic ovary and Pituitary tumor.1 mg Dexamethasone was administered orally 22:00 hours serum Cortisol level was measured the following morning at 9:00 am. Suppression of serum Cortisol to <50 nmol/l was considered to be normal. Patients with serum Cortisol of more than 50 nmol/l were further evaluated for Cushing’s syndrome.

Results: Suppression of morning Cortisol levels to <50 nmol/l occurred in 49 Obese patients. False positive rate was 2%.

Conclusion: 1 mg ODST is a valid screening test for Cushing’s in obese patients. False positive rate was 2% using a cut off point of 50 nmol/l. Our study suggested that the lack of l suppression should be investigated further and should not be considered as false positive.

Declaration of interest: There is no conflict of interest that could be perceived as prejudicing the impartiality of the research reported.

Funding: No specific grant from any funding agency in the public, commercial or not-for-profit sector.

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