Leptin, the “satiety hormone,” is a hormone made by adipose cells that helps to regulate energy balance by inhibiting hunger. Leptin is opposed by the actions of the hormone ghrelin, the “hunger hormone.” Both hormones act on receptors in the arcuate nucleus of the hypothalamus to regulate appetite to achieve energy homeostasis.
In obesity, a decreased sensitivity to leptin occurs, resulting in an inability to detect satiety despite high energy stores. People who sleep fewer than 6 hours at night are more likely to be overweight—and show reduced levels of the appetite-suppressing hormone leptin, along with elevated levels of hunger-stimulating hormone ghrelin.
Leptin also has other important physiological functions, such as regulating reproductive function, immune function, and bone metabolism.