FGF-21

Fibroblast Growth Factor 21 (FGF-21)

Evidence & Status

  • Preliminary / Experimental
  • Preliminary

At a Glance

A metabolic hormone produced by the liver that regulates fat metabolism, insulin sensitivity, and energy balance, and is elevated naturally during fasting. Studied for its therapeutic potential in non-alcoholic steatohepatitis (NASH/MASH), metabolic syndrome, and dyslipidemia.

Plain English

Researchers study FGF-21 because it is a natural hormone the liver releases during fasting or metabolic stress that helps the body switch between energy sources and manage fat metabolism. Scientists are interested in its broad metabolic effects — reducing liver fat, improving insulin sensitivity, lowering triglycerides, and potentially supporting healthy body weight. Because non-alcoholic fatty liver disease is a rapidly growing health concern, FGF-21 analogs and receptor agonists are in active pharmaceutical development, with several compounds in late-stage clinical trials.

Overview

FGF-21 is an atypical member of the fibroblast growth factor family that functions as an endocrine hormone rather than a classical paracrine growth factor. Native human FGF21 participates in metabolic signaling through FGFR/KLB receptor complexes. Engineered and long-acting FGF21 analogs are separate research entities: LY2405319 is an engineered FGF21 variant, and human studies of LY2405319, pegozafermin, efruxifermin, or other analogs must not be presented as direct evidence for native FGF21. Native FGF21 remains investigational, with no approved therapeutic product or established clinical dosing.

Research Summary

Native FGF21 is an endogenous metabolic hormone under investigation for its role in energy and lipid metabolism. Human therapeutic findings from engineered agents must remain separate: PMID 23536797 establishes LY2405319 as an engineered FGF21-based variant, and PMID 24011069 reports a human study of that LY2405319 analog rather than native FGF21. Pegozafermin, efruxifermin, and other long-acting analogs are likewise not direct native-FGF21 evidence. Native FGF21 has no approved therapeutic product or established clinical dosing.

Research Areas

  • NASH/MASH
  • Insulin resistance
  • Lipid metabolism
  • Obesity
  • Longevity
  • Brown adipose tissue
  • Cardiovascular risk

Safety & Risks

Serious Risks

  • Potential bone mineral density reduction with sustained exposure (observed in preclinical models; monitored in trials); long-term safety profile under evaluation

Reported Side Effects

  • Hypoglycemia (mild, uncommon)
  • Bone loss concerns (preclinical data — FGF-21 suppresses IGF-1 signaling in bone)
  • Nausea
  • Weight loss (in some trials, a desired effect)
United States
Investigational; native FGF21 is not approved as a therapeutic drug.
United Kingdom
Investigational; native FGF21 is not approved as a therapeutic drug.
Australia
Investigational; native FGF21 is not approved as a therapeutic drug.
Canada
Investigational; native FGF21 is not approved as a therapeutic drug.

Citations & Sources