FGF21 (Fibroblast Growth Factor 21)
DEFGF21 (Fibroblasten-Wachstumsfaktor 21)
FGF21 (fibroblast growth factor 21) is a hormone, mostly made by your liver. It is released in response to fasting, low protein intake, and mitochondrial stress. It acts on tissues through a receptor combo (FGFR1c plus β-Klotho). Its effects: it boosts fat-burning and ketone production, makes you more insulin-sensitive, and dials down the growth hormone/IGF-1 axis. The longevity link is intriguing but two-sided. Mice engineered to overproduce FGF21 live substantially longer (Zhang 2012: about 30% longer in males, 39% in females), with better metabolic health. Yet in humans, high blood FGF21 is paradoxically tied to metabolic disease and frailty. That likely reflects the body cranking out FGF21 as a stress response, rather than FGF21 directly causing aging. Drug versions (FGF21 analogues) are in development for metabolic liver disease.
Last reviewed:
This definition is educational and is not medical advice, a diagnosis, or treatment. Talk to a doctor about any health decisions. Read our full medical disclaimer