HPA Axis and Adrenal Stress Response

Most stress physiology is invisible until the response fails. A person with adequate adrenal reserve increases cortisol when infection, surgery, trauma, fever, vomiting, or psychological strain raises demand. Cortisol supports glucose availability, vascular responsiveness, and restraint of inflammation; if the HPA axis is suppressed or the adrenal cortex cannot respond, the same stressor can produce weakness, hypoglycaemia, hypotension, and shock. The bedside assessment therefore links the trigger, steroid exposure, perfusion, glucose, and electrolytes rather than treating fatigue as an isolated symptom. The cellular signal—CRH and AVP to ACTH to cortisol—becomes clinically useful when it explains why a routine illness can become an adrenal emergency.