Although acute FGF19-FGFR4/β-Klotho signaling enhances adenosine monophosphate-activated protein kinase (AMPK)-driven glucose utilization, chronic elevation induces insulin-like growth factor 1 (IGF-1) resistance that disrupts myocyte hypertrophy—a key process in sarcopenia progression (43). Here, FGFR4 is linked to sarcopenia.