Glucocorticoids and GRα Signaling in Critical Illness: Phase-Specific Homeostatic Corrections Across Systems.

Glucocorticoid (GC)-activated glucocorticoid receptor α (GRα) signaling-underpins survival and recovery during severe physiological stress. Rooted in evolution, these adjustments are not mere damage control; they constitute a coordinated, dynamic, phase-specific program that integrates metabolic, immune (innate and adaptive), cardiovascular, neuroendocrine, and organ functions. By boosting mitochondrial energy production and regulating inflammatory and hemostatic pathways, the GC-GRα axis enables adaptation to the demands of critical illness. These mechanisms operate across tissues and time to sustain systemic stability. This program unfolds in three phases. In the priming phase, innate immunity is rapidly mobilized, bioenergetic reserves are secured, and cardiovascular function is enhanced to build resilience. With the immediate threat contained, the modulatory phase suppresses excessive inflammation and oxidative stress and restores and preserves vascular integrity. In the restorative phase, resolution of injury enables structural and functional repair, re-establishing tissue architecture and function for long-term recovery. Failure to enter or complete the modulatory phase prolongs dysregulated responses that impede recovery. GRα is central: beyond anti-inflammatory actions, it shapes pro-inflammatory and metabolic programs. Through context-dependent co-regulation with nuclear factor-κB and activator protein-1, GRα directs cell-specific responses, drives chromatin remodeling, and orchestrates phase-specific gene expression to maintain a dynamic balance essential for survival. When transition to the modulatory phase fails, persistent stress signaling depletes neuroendocrine reserves, impairs bioenergetics, and exhausts key micronutrients, increasing allostatic load and mortality risk. Clinical modifiers-including critical illness-related corticosteroid insufficiency (CIRCI), mitochondrial dysfunction, hypovitaminosis, and oxidative stress-accelerate metabolic strain and decline toward organ failure. Mechanism-aligned care targeting GRα and synchronizing therapy with recovery phases enables individualized CIRCI correction, tempering of dysregulated inflammation, and organ recovery. Recognizing GC-GRα as the coordinator of homeostatic corrections highlights its evolutionary importance and guides strategies that complement the body's capacity to restore homeostasis.