Ghrelin

Definition

Ghrelin is a hormone produced primarily in the stomach that stimulates appetite and plays a crucial role in energy balance. It is often referred to as the 'hunger hormone' because it signals the brain to promote feelings of hunger, especially before meals. Ghrelin levels rise before eating and fall after meals, indicating its direct involvement in the digestive process and overall metabolism.

5 Must Know Facts For Your Next Test

1. Ghrelin is secreted mainly by the stomach's enteroendocrine cells and its levels fluctuate throughout the day based on eating patterns.
2. It not only stimulates appetite but also influences gastric motility and the release of growth hormone from the pituitary gland.
3. The rise in ghrelin levels typically occurs in anticipation of food intake, preparing the body for digestion.
4. Disruptions in ghrelin signaling are linked to conditions like obesity, as higher ghrelin levels can lead to increased hunger and food intake.
5. Research suggests that ghrelin may also have roles in regulating metabolism and promoting fat storage in addition to its appetite-stimulating effects.

Review Questions

• How does ghrelin interact with the hypothalamus to influence appetite regulation?
  • Ghrelin interacts with the hypothalamus by binding to specific receptors, which triggers signaling pathways that promote hunger. When ghrelin levels rise, particularly before meals, it activates neurons in the hypothalamus responsible for initiating the feeling of hunger. This interaction is crucial for maintaining energy balance and ensuring that the body receives adequate nourishment.
• Discuss the relationship between ghrelin and leptin in regulating body weight and appetite.
  • Ghrelin and leptin work in tandem to regulate body weight and appetite through opposing actions. Ghrelin promotes hunger by signaling to the brain when energy intake is low, while leptin inhibits appetite when energy stores are sufficient, primarily through adipose tissue signaling. A balanced interplay between these two hormones is essential for maintaining healthy body weight; imbalances can lead to conditions such as obesity.
• Evaluate how disturbances in ghrelin signaling might contribute to obesity and other metabolic disorders.
  • Disturbances in ghrelin signaling can lead to heightened feelings of hunger and increased food intake, contributing to obesity. When ghrelin levels remain elevated or are not properly regulated, individuals may experience constant cravings, leading to excessive calorie consumption. This hormonal imbalance can also affect metabolism by promoting fat storage instead of energy expenditure, which exacerbates metabolic disorders like insulin resistance and type 2 diabetes.

Related terms

Leptin: A hormone produced by adipose (fat) tissue that helps to regulate energy balance by inhibiting hunger, essentially acting as a counterpart to ghrelin.

Hypothalamus: A region of the brain that plays a key role in regulating various physiological processes, including hunger, thirst, and body temperature, and is significantly influenced by ghrelin levels.

Obesity: A medical condition characterized by excessive body fat accumulation that can result from an imbalance between energy intake and energy expenditure, often influenced by hormones like ghrelin and leptin.