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evidence · mechanism · dose
Experimental/Metabolic / GLP-1Research peptide

Retatrutide

aka LY3437943

Investigational triple agonist of GLP-1, GIP, and glucagon receptors with the largest weight-loss signal to date.

Educational explainer of a research peptide. Profiles in this section deliberately omit clinical-trial citations, dosing protocols, and purchase links. Not FDA-approved as a supplement; not a recommendation to use.

Overview

Retatrutide is a single-molecule triple agonist of GLP-1, GIP, and glucagon receptors, currently in late-stage trials.

Source
  • Recombinant and chemical synthesis
Forms
  • Weekly subcutaneous injection (trial protocols)

Mechanism of action

Activates GLP-1 and GIP receptors for insulin and satiety effects and additionally activates the glucagon receptor to increase energy expenditure and hepatic fat oxidation.

Pathways
  • · GLP-1, GIP, glucagon receptor agonism
Receptors
  • · GLP-1 receptor
  • · GIP receptor
  • · Glucagon receptor
Hormones
  • · Insulin
  • · Glucagon

How it acts on the body

Where semaglutide and tirzepatide rely on satiety and insulin, retatrutide adds glucagon-receptor agonism — which raises basal energy expenditure and accelerates hepatic fat oxidation. The result in phase 2 trials is weight loss that exceeds either GLP-1 alone or GIP/GLP-1 combinations.

The glucagon arm is also the most novel risk. Glucagon raises hepatic glucose output, so the net glycemic effect depends on insulin response keeping pace; trial data so far show net A1c improvement, but the long-term safety of sustained tri-agonism is still being characterized.

Hormonal & endocrine impact

How this peptide is reported to shift specific hormones and signaling molecules. Directionality reflects research literature and preclinical models, not clinical prescribing data.

Projected hormonal trajectory
Illustrative curves derived from reported direction of effect. Not measured patient data.

Curves are schematic shapes (sigmoid for increases/decreases, damped oscillation for modulation/stabilization) anchored to a 100% baseline. They communicate direction and tempo of change reported in research literature — not absolute hormone concentrations.

InsulinIncreases
Glucose-dependent insulin secretion.
Glucagon signalingIncreases
Direct receptor agonism elevates basal metabolic rate.
GIP signalingIncreases
Adds adipose-tissue effects beyond GLP-1.
Leptin sensitivityModulates
Improves with weight loss.

Effects on the body

Decreases
Body weight (largest documented for peptide therapy)
Increases
Resting energy expenditure
Supports
Hepatic fat oxidation

Organ system effects

Endocrine

Tri-agonist control of glucose and energy partitioning.

Liver

Increased fat oxidation via glucagon arm.

Brain & CNS

Central satiety similar to other GLP-1 agents.

Reported effects

Drawn from preclinical research, anecdote, and small-scale clinical observation. No evidence grades are assigned — most peptides on this page lack rigorous human trials.

  • Largest reported peptide-driven weight loss to date
  • Improvements in MASLD/MASH markers in trials

Potential side effects

Common
  • · Nausea
  • · Diarrhea
  • · Increased heart rate
Rare
  • · Hepatic enzyme shifts
Serious
  • · Long-term safety still being studied

Drug interactions

Insulin or sulfonylureas
Hypoglycemia risk.
moderate

Pairing context

Often combined with
  • Comprehensive lifestyle program
    Compounds metabolic benefits.
Avoid combining with
  • Personal or family history of MTC or MEN2
    Class-shared contraindication.
Important. Research peptides described here are not FDA-approved supplements. Supplement Scholar does not endorse, recommend, or link to any source for purchase. Consult a qualified clinician before considering any peptide therapy.