Recombinant produced leptin receptor (SOB-R) is immobilized on a microtiter plate. The sample to be tested is diluted in dilution buffer and incubated on the microtiter plate; the leptin bound by the immobilized receptor is detected by a specific, polyclonal, Biotin-conjugated antibody and a streptavidin-conjugate. The quantification is performed with recombinant leptin, which is used as a standard and is traceable to the WHO International Standard (97/594). Sample Types: serum, plasma. Range: 0.05 - 6 ng/mL. Sensitivity: 0.01 ng/ml. Time: 4 hours ? Leptin a hormone of 146 amino acids shows a molecular weight of 16 kDa (P41159). It consists of four anti-parallel a-helices. Leptin is primarily produced by adipocytes and thus provides a signal to the energy state of the organism. By binding to the leptin receptor (P48357) it influences the activity of the JAK -STAT pathway and thereby regulates energy metabolism, especially the food intake. Leptin levels show a circadian variation (+/- 30%) and are dependent on BMI, pubertal status, and gender. In addition to the expression itself, the bioavailability of leptin, is regulated via a binding protein, as with many hormones with type I cytokine receptors. The binding protein is the extracellular domain of the Leptin receptor formed by proteolytic cleavage of the receptor be metalloproteases (ADAM 10/17).