Dexamethasone suppression test predicts later development of an impaired adrenal function after a 14-day course of prednisone in healthy volunteers.

Background: Suppression of the adrenal function after glucocorticoid treatment is common, potentially dangerous, and unpredictable. Identification of patients at risk is of clinical importance. We hypothesized that the dexamethasone suppression test predicts the development of corticosteroid-induced impaired adrenal function.

Methods: We included 39 healthy male volunteers. After a 1-microg ACTH test, all participants underwent an overnight 0.5-mg dexamethasone suppression test. Participants then took prednisone, 0.5 mg/kg body weight, for 14-day. After the withdrawal of prednisone, a 1-microg ACTH test was performed and a clinical score was assessed on days 1, 3, 7, and 21.

Results: On days 1, 3, 7, and 21, 100, 50, 26.5 and 32.4% of the participants had a suppressed adrenal function. The risk of developing suppressed adrenal function decreased from 44 to 0% in patients with cortisol levels after the administration of dexamethasone in the lowest and highest quartiles respectively. Receiver operating curve (ROC) analysis performed to predict a suppressed adrenal function on day 7 after the withdrawal of prednisone showed an area under the curve (AUC) of 0.76 (95% confidence interval (CI) 0.58-0.89) for cortisol after the administration of dexamethasone, which was in the range of the AUC of 0.78 (95% CI 0.6-0.9) for pre-intervention cortisol after the administration of ACTH. Basal cortisol before intake of prednisone (AUC 0.62 (95% CI 0.44-0.78)) and the clinical score (AUC 0.64 (95% CI 0.45-0.79)) had significantly lower AUCs.

Conclusion: Circulating cortisol levels after a dexamethasone suppression test and a pre-intervention-stimulated cortisol level are predictive of later development of a suppressed adrenal function after a 14-day course of prednisone, and are superior to a clinical score or basal cortisol levels. This may allow a more targeted concept for the need of stress prophylaxis after cessation of steroid therapy.