FGF-21 is novel metabolic regulator produced primarily by the liver. FGF-21 is a potent activator of glucose uptake on adipocytes, protects animals from diet-induced obesity when overexpressed in transgenic mice, and lowers blood glucose and triglyceride levels when therapeutically administered to diabetic rodents. This hormone contributes to body weight regulation and is strongly involved in the response to nutritional deprivation and ketogenic state in mice. The principal sites of metabolic actions of FGF21 are adipose tissue, liver and pancreas. The Mouse and Rat FGF-21 ELISA kit is a sandwich ELISA intended for the determination of FGF-21 in mouse or rat serum, plasma and cell culture medium. The assay exhibits excellent analytical characteristics and the use of biotin-labelled antibody gives the assay very good sensitivity. Recombinant mouse FGF-21 is used as a calibrator in the kit, this enables true quantification of FGF-21 in pg/ml values for mouse samples, the concentrations of FGF-21 in rat samples are expressed using artificial units (U/ml). BioVendor launched its Human FGF-21 ELISA in early 2008 and the new Mouse and Rat FGF-21 ELISA extended the research possibilities to rodent models.