The HPA axis stands for the Hypothalamic–Pituitary–Adrenal axis.
It’s a complex communication network between the brain and adrenal glands that regulates the body’s stress response, along with energy balance, immunity, digestion, and mood.
🔬 How It Works (Step by Step)
- Hypothalamus (H)
- Located in the brain.
- Detects stress (physical or psychological).
- Releases CRH (corticotropin-releasing hormone).
- Pituitary Gland (P)
- The “master gland” under the brain.
- Responds to CRH by releasing ACTH (adrenocorticotropic hormone) into the bloodstream.
- Adrenal Glands (A)
- Sit above the kidneys.
- ACTH signals them to produce cortisol (the main stress hormone) and other hormones like adrenaline.
⚡ Role of Cortisol
- Short-term stress: Boosts blood sugar, sharpens focus, mobilizes energy (fight-or-flight).
- Long-term balance: Helps regulate inflammation, immune response, blood pressure, and circadian rhythm.
⚖️ Dysregulation of the HPA Axis
When the axis is over- or under-active, problems can occur:
- Chronic stress → prolonged cortisol release, leading to anxiety, weight gain, high blood pressure, sleep disruption.
- Burnout / adrenal fatigue (controversial term) → low responsiveness of the axis, linked to fatigue and mood issues.
- Medical conditions: Cushing’s syndrome (too much cortisol), Addison’s disease (too little cortisol).
🌍 Why It’s Important
The HPA axis is essentially the body’s stress thermostat.
It helps us survive immediate threats, but when constantly “on,” it can harm long-term health. Maintaining balance through sleep, nutrition, movement, and stress management is key.
👉 In short: The HPA axis is the brain-to-adrenal stress response system, controlling cortisol and helping regulate energy, immunity, mood, and resilience to stress.