CRH, or Corticotropin-Releasing Hormone (sometimes called Corticotropin-Releasing Factor, or CRF), is a peptide hormone produced by the hypothalamus, a key brain structure that regulates the endocrine system.
CRH plays a central role in the body’s response to stress by stimulating the release of ACTH (Adrenocorticotropic Hormone) from the anterior pituitary gland.
🧠 How Does CRH Work?
The HPA Axis: Hypothalamic–Pituitary–Adrenal Axis
This is the body’s primary stress-response system.
- The hypothalamus detects a stressor and releases CRH.
- CRH travels via the hypophyseal portal system to the anterior pituitary.
- The anterior pituitary releases ACTH in response.
- ACTH then travels through the bloodstream to the adrenal glands (above the kidneys).
- The adrenal cortex produces and releases cortisol, the body’s main stress hormone.
🧪 What Does Cortisol Do?
Cortisol (released due to CRH → ACTH stimulation):
- Increases blood sugar
- Suppresses immune responses
- Aids in metabolism of fat, protein, and carbohydrates
- Helps the body respond to stress
- Affects memory, mood, and focus
🔁 Feedback Loop:
Cortisol levels feedback to the hypothalamus and pituitary:
- High cortisol → inhibits CRH and ACTH release (negative feedback)
- Low cortisol → stimulates more CRH release
This loop helps keep the stress response in balance.
🧪 Clinical Relevance of CRH
✅ CRH Is Used For:
- Diagnostic tests to assess pituitary and adrenal function (e.g., CRH stimulation test)
- Research on stress, anxiety, and depression
📉 Low CRH May Be Seen In:
- Adrenal insufficiency (secondary causes — pituitary or hypothalamic dysfunction)
- Hypopituitarism (decreased ACTH and cortisol)
📈 High CRH May Be Seen In:
- Chronic stress (linked to anxiety and depression)
- CRH-secreting tumors (rare, can cause Cushing’s syndrome)
- Post-traumatic stress disorder (PTSD) (elevated CRH but often low cortisol)
🧠 CRH and Mental Health
CRH is not only a hormone — it also acts as a neurotransmitter in the brain:
- Regulates mood, fear, and emotional response
- Overactive CRH signaling is linked to depression, anxiety, and PTSD
- A target for experimental medications aiming to modulate stress responses
🧠 Summary Table:
| Feature | CRH (Corticotropin-Releasing Hormone) |
|---|---|
| Produced by | Hypothalamus |
| Acts on | Anterior pituitary (to release ACTH) |
| Part of | HPA axis (stress-response system) |
| Stimulates | ACTH → which stimulates adrenal cortisol release |
| Controlled by | Negative feedback from cortisol |
| Associated with | Stress response, metabolism, mood, immune function |
| Clinical relevance | Tested in adrenal/pituitary disorders and psychiatric research |