Hypothalamic-Pituitary-Adrenal Axis Activity in Panic Disorder

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Abstract
Background: Oversecretion of corticotropin-releasing hormone and/or dysregulation of the hypothalamic-pituitary-adrenal (HPA) axis may contribute to patho-physiologic processes in panic disorder, but documentation of HPA axis disturbance in panic has been inconsistent. In the current study we examined HPA axis activity in panic disorder over a full circadian cycle, using frequent blood sampling to provide detailed assessment of corticotropin and cortisol secretion. Methods: Twenty patients with panic disorder and 12 normal control subjects were studied. Blood samples were drawn every 15 minutes for 24 hours and assayed for corticotropin and cortisol levels. Results: Patients with panic disorder had elevated overnight cortisol secretion and greater amplitude of ultradian secretory episodes. Patients who entered the study through clinical referral channels had greater cortisol secretion than those recruited by advertisements. Patients with panic disorder who had a low frequency of panic attacks had elevated daytime corticotropin levels and elevated corticotropin ultradian amplitude. Patients with a high frequency of attacks had shifted corticotropin circadian cycles. Conclusions: Patients with panic disorder demonstrate subtle alterations in HPA axis activity, characterized by overnight hypercortisolemia and increased activity in ultradian secretory episodes, but HPA axis alterations in panic are modulated by illness severity and treatment seeking. It remains unclear whether HPA axis dysregulation in panic represents a pathogenic defect within the axis itself. Inconsistencies in prior work may reflect the subtlety of the abnormalities seen, differences in clinical characteristics of patients studied, and the use of different probes and measurement contexts.