Clinical endocrinology
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Clinical endocrinology · May 1998
Comparative StudyThe low-dose dexamethasone suppression test in patients with adrenal incidentalomas: comparisons with clinically euadrenal subjects and patients with Cushing's syndrome.
Increasing evidence favours subtle glucocorticoid excess in many patients with adrenal incidentalomas. However, existing evidence is based mainly on the overnight dexamethasone suppression test, a test that is commonly abnormal even among clinically euadrenal subjects. The aim of the present study was to evaluate patients with adrenal incidentalomas for subtle glucocorticoid excess by the more specific low-dose dexamethasone test (LDDST). Moreover, since the criteria of what constitutes an abnormal cortisol response following this test have been largely anecdotal, we report our results in comparison with those obtained in clinically euadrenal subjects, and patients with Cushing's syndrome. ⋯ On the basis of our data in a large group of clinically euadrenal subjects, we suggest that following LDDST cortisol concentrations should become undetectable with the currently used radioimmunoassays. In patients with adrenal incidentalomas, application of the LDDST confirmed the presence of incomplete suppression of cortisol in the majority of patients. We suggest that the LDDST is a sensitive index of autonomous cortisol production in patients with adrenal incidentalomas; following this test a grading of subtle glucocorticoid excess may be obtained but future studies correlating biochemical, clinical and epidemiological data are required, in order to develop widely agreed cut-off levels of clinically significant glucocorticoid excess in these patients.