Inter-Organ Communication Networks in Systemic Physiology: Glucocorticoid Receptor α as a Central Integrator of Homeostasis.

The survival of complex multicellular organisms depends on continuous inter-organ communication networks that coordinate organism-wide responses across physiological conditions and stress states, including adaptation to environmental challenges, infection, and injury. Rather than operating as isolated units, organ systems are integrated through interconnected signaling networks that transmit biological information across tissues. Building on prior work examining individual physiological pathways, this review introduces a unified systems-level framework that integrates inter-organ communication into a coherent model of organism-wide regulation. This review proposes a systems-level framework in which homeostasis is maintained through eight principal communication systems: neural, endocrine, immune-inflammatory, vascular, lymphatic, metabolic, microbiome-gut, and mechanical-structural. Epithelial barriers function as dynamic signaling interfaces within multiple systems, while extracellular vesicles act as cross-system mediators of information transfer rather than as independent communication networks. These systems operate across distinct temporal scales to coordinate host defense, metabolic adaptation, vascular regulation, and tissue repair. The framework further introduces a temporal hierarchy of signaling dynamics that links communication systems to phase-specific responses during physiological stress. Within this integrated network, glucocorticoid receptor α (GRα) is proposed to function as a systems-level regulator of inter-organ communication, supported by converging mechanistic, experimental, and clinical evidence, with variability in the strength of evidence across domains. In contrast to prior reviews, which addressed GRα function within individual systems, this work conceptualizes GRα as a central rheostat coordinating cross-system signaling and temporal transitions in homeostatic correction. Evidence was identified through hypothesis-driven searches using the Consensus AI platform and verified through manual review of primary biomedical literature. GRα, a ligand-activated transcription factor expressed in most nucleated cells, enables hormonal stress signals to coordinate gene-expression programs across tissues, modulating neuroendocrine responses, endothelial function, inflammatory signaling, metabolic regulation, microbiome-host interactions, and tissue remodeling. Systemic responses to stress progress through three phases of homeostatic correction-Priming, Modulatory, and Restorative-within which GRα supports integrated organism-wide adaptation. This integrative framework provides a mechanistic basis for understanding the emergence and temporal evolution of biological responses in health and critical illness.