This assay kit provides the convenience of an all-inclusive cell-based reporter assay system for FGFR4/β-Klotho endocrine FGF signaling. In addition to Reporter Cells, included are an optimized culture medium for use in reviving the cryopreserved cells, a culture medium for use in preparing test sample treatments, the physiological endocrine activator FGF-19, Luciferase Detection Reagents, and a cell culture-ready assay plate. To re-iterate, this assay is primarily focused on the endocrine signaling activities of FGFR/FGFs.