Searchable abstracts of presentations at key conferences in endocrinology
Endocrine Abstracts (2009) 20 P34

ECE2009 Poster Presentations Adrenal (54 abstracts)

The utility of the low dose dexamethasone suppression test in patients diagnosed with an adrenal incidentaloma

Miguel Debono , Charlotte Durrington , Scott Williams & John Newell-Price

Academic Unit of Diabetes, Endocrinology & Metabolism, University of Sheffield, Sheffield, UK.

Objective: The diagnosis of subclinical Cushing’s syndrome in patients with incidentalomas is not always straight forward and a number of different criteria have been used. The 1 mg overnight dexamethasone suppression test has been recommended as a screening test, followed up by other tests of the hypothalomo–pituitary–adrenal axis to confirm the diagnosis. In this study we investigate whether the low-dose dexamethasone suppression test offers additional information to the overnight dexamethasone suppression test in establishing diagnosis.

Design: Retrospective, observational study.

Patients and measurements: Demographic and clinical data were collected on 137 patients diagnosed with incidentalomas. A full endocrinology work up was performed.

Results: There were 76/137 (55%) patients who had either a positive overnight dexamethasone suppression test or/and a low-dose dexamethasone suppression test. 60/103 (58%) patients were found to have a positive overnight dexamethasone test whilst 45/63 (71%) patients had a positive low-dose dexamethasone test. 29 patients had both tests done of which 20/21 patients with a cortisol level >70 nmol/l after the overnight dexamethasone test had a positive low-dose dexamethasone test, whilst the other 8 patients, all of which had a cortisol level <70 nmol/l post-overnight dexamethasone test, had a negative low-dose dexamethasone test. Correlation analysis revealed a significant positive correlation between cortisol levels for both tests (r=0.78; P<0.001). Mean cortisol levels after each test were similar (103 vs 104.8 nmol/l; P=0.9).

Conclusion: We have established that in patients with a cortisol level of >70 nmol/l after an overnight dexamethasone test, the low-dose dexamethasone suppression test is usually positive and will not offer more information than the overnight dexamethasone suppression test in the diagnostic work-up of subclinical Cushing’s syndrome.

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