Leptin is a hormone that affects most of the body functions, be it is immune system, appetite or energy metabolism. Leptin is also known as 'obesity hormone', 'starvation hormone' and 'fat hormone.' Its main targets are in certain hypothalamic zones. Others have been identified: ovaries, adiposities, liver, hematopoietic cells and langhéransiennes tissues. Leptin is produced and secreted into the bloodstream by adipose cells (adiposities) permanently and in large quantities, depending on the volume of the fatty tissue, making it possible to reach equilibrium (the 'right weight', called set point by the researchers). Looking at the effect of leptin on weight many weight management pills available these days contain leptin. The leptin-human test is the test to evaluate leptin level in blood.