Which hormone has an antagonistic effect to ghrelin, promoting a feeling of fullness?

• A. Insulin
• B. Leptin
• C. Testosterone
• D. Cortisol

Answer: (B)

Leptin is a hormone produced by adipose (fat) tissue that plays a crucial role in regulating energy balance and body weight. One of its primary functions is to signal satiety, or the feeling of fullness, to the brain. When fat stores increase, leptin levels rise, leading to decreased appetite and increased energy expenditure. This action is antagonistic to ghrelin, which is often referred to as the "hunger hormone," as it stimulates appetite and promotes food intake.

The relationship between leptin and ghrelin illustrates a homeostatic mechanism that helps maintain energy balance in the body. When you consume food, ghrelin levels decrease, while leptin levels increase, contributing to a sense of fullness and reducing the desire to eat.

While insulin is involved in glucose metabolism and does have a role in signaling satiety, it does not act as the primary antagonist to ghrelin like leptin does. Testosterone and cortisol are hormones that influence various metabolic processes but are not primarily responsible for regulating hunger and satiety in opposition to ghrelin. Therefore, leptin is considered the principal hormone that promotes feelings of fullness effectively countering ghrelin's appetite-stimulating effects.