Ghrelin
Also known as: Hunger hormone, Lenomorelin
Ghrelin is a peptide hormone primarily produced in the stomach that stimulates appetite and promotes growth hormone release. Known as the 'hunger hormone,' ghrelin signals to the brain to increase food intake and plays a role in energy homeostasis. Several research peptides mimic ghrelin's GH-releasing effects.
Last updated: January 21, 2026
How Ghrelin Works
Ghrelin has multiple functions in the body:
Appetite Regulation
- Stomach produces ghrelin when empty
- Ghrelin crosses blood-brain barrier
- Binds to hypothalamic receptors (GHS-R)
- Triggers hunger signals and food-seeking behavior
- Levels drop after eating
Growth Hormone Release
- Ghrelin binds to pituitary GHS-R
- Stimulates GH release independently of GHRH
- Works synergistically with GHRH
Ghrelin Patterns
| Situation | Ghrelin Level |
|---|---|
| Before meals | High (triggers hunger) |
| After meals | Low (suppressed) |
| Sleep deprivation | Elevated |
| Chronic dieting | Elevated |
| After weight loss | Elevated (promotes regain) |
Ghrelin Receptor (GHS-R)
The growth hormone secretagogue receptor is the target for:
- Natural ghrelin
- GHRP peptides (GHRP-6, GHRP-2)
- Ipamorelin
- MK-677 (non-peptide agonist)
These compounds are called “ghrelin mimetics” because they activate the same receptor.
Ghrelin Mimetics in Research
GHRP-6
- Potent ghrelin receptor agonist
- Strong GH release
- Significant appetite increase
- Some cortisol elevation
Ipamorelin
- Selective GHS-R agonist
- Minimal appetite increase
- Little effect on cortisol
- “Cleaner” GH release profile
MK-677 (Ibutamoren)
- Non-peptide ghrelin mimetic
- Orally active
- Long-lasting effects
- Increases appetite
Ghrelin vs GHRH Pathway
Both pathways stimulate GH release but differently:
| Aspect | Ghrelin/GHS-R | GHRH/GHRH-R |
|---|---|---|
| Primary trigger | Empty stomach | Hypothalamic rhythm |
| Effect type | Initiates GH pulse | Amplifies GH pulse |
| Appetite effect | Increases | None |
| Mechanism | Calcium signaling | cAMP signaling |
Ghrelin and Weight Management
Ghrelin presents challenges for weight loss:
- Before weight loss: Normal ghrelin patterns
- During calorie restriction: Ghrelin increases
- After weight loss: Ghrelin remains elevated
- Result: Persistent hunger signals promoting weight regain
This is why sustained weight loss is challenging—the body increases ghrelin to restore previous weight.
Frequently Asked Questions
Why do I feel hungry at regular meal times?
Ghrelin release becomes conditioned to your eating schedule. Your body learns when to expect food and releases ghrelin in anticipation. This is why hunger often comes at regular intervals even if you ate more or less than usual.
Do ghrelin-mimetic peptides make you hungry?
It depends on the specific compound. GHRP-6 significantly increases appetite. Ipamorelin has minimal appetite effects despite working on the same receptor, due to different selectivity profiles.
Can you lower ghrelin to reduce hunger?
Ghrelin levels naturally drop after eating, especially with protein-rich meals. Sleep and stress management also help regulate ghrelin. Some bariatric surgeries reduce ghrelin by removing part of the stomach where it’s produced.
Related Peptides
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Disclaimer: This glossary entry is for educational purposes only and does not constitute medical advice. Always consult a qualified healthcare provider for medical questions.