247. HPA axis response to graded exercise in atypical depression

Abstract

We studied the pituitary-adrenal/catecholaminergic response to a naturalistic stressor in atypical depression. Eleven patients with atypical depression (DSM-IV) and 11 controls had their ACTH, cortisol and norepinephrine responses measured during a graded exercise session. This is a unique tool because well conditioned athletes who had to work harder to reach 90% of their individual maximal oxygen utilization capacity (VO2max) showed similar stress responses compared to untrained individuals despite the fact that untrained individuals expended much less work to reach their 90% VO2max. ANOVA with repeated measures showed a significant time by group interaction (F = 2.69, df = 7, p < 0.01), depicting both the overall increased ACTH output and the delayed response pattern in the patient group. Immediate post exercise AUC was significantly greater in patients (217 ± 38 vs. 120 ± 30, p < 0.05). Patients ACTH response at time 30 min was greater than the response seen in controls at the same time point (101.2 ± 20.5 vs. 48.9 ± 14.3, p < 0.05). Baseline plasma cortisol level, total AUC and, immediate post exercise AUC did not differ between groups. Plasma levels of norepinephrine did not differ in the variables used to measure response to exercise (total AUC, baseline, peak and pattern of response). The elevated and delayed ACTH response and no change in the cortisol response in the patient group compared to matched controls reinforce the hypothesis of a hypoactive hypothalamic-pituitary-adrenal axis in atypical depression.