hypothalamic-pituitary-adrenal axis recovery following the 1-mg overnight dexamethasone suppression test in healthy volunteers

Background: the recovery of hypothalamic-pituitary-adrenal (hpa) axis suppression following pharmacological doses of various steroids has been studied previously. however, no study has been conducted using the more commonly used 1-mg dexamethasone in the overnight dexamethasone suppression test (odst). hence, we aimed at evaluating hpa axis recovery after the 1-mg odst. objectives: this study aimed at investigating the pattern and time of recovery of the hpa axis following the 1-mg odst in healthy subjects. methods: ten healthy volunteers aged 18 - 40 years, bmi < 30 kg/m^2, with neither exposure to steroids nor interfering drugs were included. the 1-mg odst was performed, and the adrenocorticotropic hormone (acth) and cortisol samples were withdrawn at regular intervals. the serum cortisol of < 1.8 µg/dl was considered as hpa axis suppression, whereas the cortisol value equal to or more than baseline was deemed as recovery. results: cortisol and acth levels were suppressed in all subjects 9 hours following the 1-mg odst. although acth showed an early increase after 8 hours, the upsurge was noticed following 24 hours (mean ± sd, 34.42 ± 18 pg/ml). later, cortisol accompanied acth, and both reached their baseline after 72 hours (mean ± sd, acth, 37.48 ± 12.44 pg/ml; cortisol, 8.45 ± 3.32 μg/dl). a small dip in acth and cortisol (mean acth, 23.84 pg/ml; mean cortisol, 2.3 μg/dl) was observed after 24 - 36 hours indicating the return of the diurnal rhythm before complete recovery. conclusions: the complete recovery of the hpa axis occurs only 72 hours following the 1-mg odst. acth begins to recover as early as 8 hours after the maximal suppression and diurnal rhythm of acth and cortisol resume 24 to 36 hours later.