Leptin

Patent Granted Leptin (from Greek λεπτός leptos, "thin"), the "satiety hormone", is a hormone made by fat cells which regulates the amount of fat stored in the body. It does this by adjusting both the sensation of hunger, and adjusting energy expenditures. Hunger is inhibited (satiety) when the amount of fat stored reaches a certain level. Leptin is then secreted and circulates through the body, eventually activating leptin receptors in the arcuate nucleus of the hypothalamus. Energy expenditure is increased both by the signal to the brain, and directly via leptin receptors on peripheral targets. The effect of leptin is opposite to that of ghrelin, the "hunger hormone". Ghrelin receptors are on the same brain cells as leptin receptors, so these cells receive competing satiety and hunger signals.