Figure 34.3
The appetite hormones

Ghrelin: Hormone secreted by empty stomach; sends “I’m hungry” signals to the brain.

Insulin: Hormone secreted by pancreas; controls blood glucose.

Leptin: Protein hormone secreted by fat cells; when abundant, causes brain to increase metabolism and decrease hunger.

Orexin: Hunger-triggering hormone secreted by hypothalamus.

PYY: Digestive tract hormone; sends “I’m not hungry” signals to the brain.