Endocrine Abstracts

Background: Neither dosage nor duration of systemic glucocorticoid therapy are reliable indicators of subsequent adrenal insufficiency. The dexamethasone suppression test is a measure of feedback sensitivity of the hypothalamic–pituitary–adrenal axis to cortisol. We hypothesized that this test predicts the later development of an adrenal insufficiency after a 14 days’ course of oral prednisone in healthy volunteers.

Methods: We analyzed data from 13 healthy males from a total of 30 who will be included in this prospective observational study. After getting routine laboratory tests, including a low dose (1-μg) cosyntropin test, all participants underwent an overnight 0.5 mg dexamethasone suppression test. All subjects then took 0.5 mg/kg prednisone for 14 days. A low dose (1-μg) cosyntropin test was performed on day 1, 3, 7, and 21 after withdrawal to asses adrenal axis function.

Results: Cortisol levels after the dexamethasone suppression test significantly correlated with cortisol levels after low dose cosyntropin testing on day 7 (r=0.646, P=0.02). In patients with a cortisol level after dexamethason < 35 nmol/l or ≥35 nmol/l, respectively, median cortisol levels after low dose cosyntropin testing were significantly lower on day 3 (495 nmol/l (IQR 446.5–518.75) vs 593 nmol/l (IQR 563–646), P=0.015) and day 7 (494 nmol/l (IQR 474–532.75) vs 690 nmol/l (IQR 619.5–722.5), P=0.002). A suppressed adrenal function occurred in 87.5 and 83.3% on days 3 and 7, respectively in participants with a cortisol level after dexamethasone < 35 nmol/l as compared to 22.2 and 0%, respectively when cortisol after dexamethasone was ≥ 35 nmol/l (P=0.007 and P=0.002).

Conclusion: Cortisol levels after a 0.5 mg dexamethasone suppression test predict the development of a suppressed adrenal function at days 3 and 7 after a 14 days’ course of oral prednisone. With this information a more targeted concept for the need of stress prophylaxis after cessation of steroid therapy can be envisioned.