Which hormone is primarily responsible for stimulating hunger?

The hormone primarily responsible for stimulating hunger is ghrelin. It is often referred to as the "hunger hormone" because it plays a crucial role in signaling the brain to increase appetite when the stomach is empty. Ghrelin is produced primarily in the stomach and levels of this hormone increase before meals and decrease after eating. This signaling mechanism helps regulate energy balance and motivates food intake, making it integral to understanding how hunger is biologically controlled.

In contrast, leptin is associated with appetite suppression and energy expenditure, while cortisol is a stress hormone that can influence eating behavior under specific conditions. Insulin, on the other hand, is involved in glucose metabolism and also plays a role in signaling satiety after meals. Therefore, ghrelin's direct influence on hunger makes it the key hormone in this context.