Leptin

Leptin is the product of the "ob" gene, originally identified in abnormally obese mice. The gene acts as a hormone, binding to a specific site in the brain. Leptin appears to function in mice in sensing the amount of fat stored in adipocytes and controlling Feeding behavior appropriately. Mice lacking leptin become very fat from overeating. In humans, the function of leptin is less clear, as obese people frequently have large amounts of leptin.

See also: Biochemistry of Obesity, Serotonin