The stress hormone system in various sleep disorders

Area of Science:

• Neuroendocrinology
• Sleep Medicine
• Chronobiology

Background:

• The hypothalamic-pituitary-adrenal (HPA)-system, crucial for stress response, is modulated by circadian rhythms and sleep.
• Conflicting data exist regarding HPA-system activity in sleep disorders.
• The dexamethasone/corticotropin-releasing-hormone (DEX/CRH) test, a sensitive measure of HPA-system feedback, had not been used in sleep disorder research.

Purpose of the Study:

• To investigate HPA-system activity and negative feedback sensitivity in patients with obstructive sleep apnea (OSA), restless legs syndrome (RLS), and primary insomnia.
• To assess the dynamic response of the HPA-system using the DEX/CRH test in sleep disorder populations compared to healthy controls.

Main Methods:

• Utilized the DEX/CRH test, combining dexamethasone suppression and CRH stimulation, to dynamically assess the HPA-system.
• Studied 25 OSA patients, 18 RLS patients, 21 primary insomnia patients, and 33 healthy controls.
• Measured adrenocorticotropic hormone (ACTH) and cortisol levels post-suppression and post-stimulation.

Main Results:

• No significant differences in the number of non-suppressors were found among groups, indicating normal HPA-axis negative feedback sensitivity.
• RLS patients showed slightly lower ACTH levels, but cortisol levels were similar across all groups after dexamethasone suppression.
• Following CRH stimulation, no differences in ACTH or cortisol levels were observed, and adrenocortical responsiveness to ACTH was comparable between groups.

Conclusions:

• This study provides the first evidence of normal HPA-system feedback sensitivity in patients with OSA, RLS, and primary insomnia.
• The findings suggest that sleep disorders are unlikely to be the primary cause of HPA-system abnormalities observed in affective disorders.