Ghrelin (Ghl)
Ghrelin (Ghl): The Hunger Hormone and Its Role in Appetite Regulation
Ghrelin (Ghl), often referred to as the “hunger hormone,” is a peptide hormone primarily produced by the stomach, with smaller amounts released by the small intestine, pancreas, and brain. It plays a crucial role in regulating appetite, energy balance, and metabolism. Below is an overview of ghrelin’s functions, its relationship with obesity, and its clinical significance.
Functions of Ghrelin
Appetite Regulation:
- Ghrelin signals the hypothalamus in the brain when the stomach is empty, stimulating hunger and increasing food intake[3][6].
- Levels rise before meals and decrease after eating[4][6].
Energy Balance:
- Promotes fat storage and reduces metabolic rate, helping the body conserve energy during fasting or caloric restriction[5][6].
Other Roles:
- Influences reward-seeking behavior, taste sensation, and sleep-wake cycles[3][4].
- Stimulates growth hormone secretion via its effects on somatotroph cells in the pituitary gland[1].
Ghrelin and Obesity
Ghrelin Levels in Obesity:
- Contrary to expectations, ghrelin levels are typically lower in individuals with obesity compared to lean individuals[4][6].
- However, people with obesity may have increased sensitivity to ghrelin or an overactive ghrelin receptor (GHS-R), leading to heightened hunger despite lower circulating levels[3][5].
Impact on Weight Loss:
- Diet-induced weight loss increases ghrelin levels as a defense mechanism against starvation, making it harder to maintain weight loss[3][4][5].
Therapeutic Potential:
- Ghrelin receptor antagonists or inverse agonists are being explored as anti-obesity treatments to block hunger signals and reduce calorie intake[1][5].
Clinical Significance
Conditions Associated with High Ghrelin Levels:
- Prader-Willi syndrome: Characterized by severe obesity and extreme hunger due to elevated ghrelin levels[4].
- Cachexia and anorexia nervosa: High ghrelin levels may stimulate appetite as a compensatory response to weight loss[4].
Effects of Bariatric Surgery:
- Gastric bypass surgery reduces ghrelin production by shrinking the stomach, leading to decreased hunger and aiding weight loss[5].
- Chronic stress increases ghrelin secretion, contributing to stress-related overeating and weight gain[8].
Conclusion
Ghrelin is a key regulator of hunger and energy balance, playing a significant role in both normal physiology and metabolic disorders like obesity. Understanding its mechanisms has opened avenues for developing targeted therapies to manage obesity and related conditions.
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References
- Title: The Role of Ghrelin in Appetite Regulation and Body Weight Control
DOI: 10.1111/j.1467-789X.2006.00270.x
Summary: This review explores the interplay between ghrelin and leptin in regulating food intake and body weight, highlighting their roles in appetite signaling and energy balance. - Title: Targeting the Ghrelin Receptor for Obesity Management
DOI: 10.3390/ijms18020273
Summary: Discusses the potential of ghrelin receptor antagonists as therapeutic agents for obesity, focusing on their mechanisms of action and clinical implications. - Title: Ghrelin and Its Role in Stress-Induced Eating Behaviors
DOI: 10.1210/en.2019-00347
Summary: Examines the role of ghrelin in stress-related overeating, with insights into its effects on reward pathways and emotional eating.
