DeSoto Peptides Research Journal | October 2026
Metabolic research has changed dramatically with the development of medications and investigational compounds that target hormones involved in appetite, glucose regulation, and energy balance.
Three names have become particularly important in this field: Semaglutide, Tirzepatide, and Retatrutide.
Although all three influence the GLP-1 signaling system, they are not identical.
Semaglutide targets one major hormone receptor. Tirzepatide activates two. Retatrutide introduces a third receptor associated with glucagon signaling.
This progression has raised important scientific questions about whether targeting multiple hormone pathways produces different effects on body weight, energy expenditure, glucose metabolism, and metabolic health.
Understanding the differences requires examining both the underlying mechanisms and the clinical evidence.
Understanding GLP-1 and Metabolic Hormone Research
GLP-1, or glucagon-like peptide-1, is a hormone involved in glucose regulation and appetite signaling.
It is released by specialized intestinal cells in response to nutrient intake.
GLP-1 influences several biological functions:
Glucose-dependent insulin secretion
Appetite regulation and satiety
Gastric emptying
Communication between the digestive system and brain
Post-meal glucose control
Researchers have developed GLP-1 receptor agonists to investigate and modify these pathways.
However, GLP-1 represents only one component of metabolic hormone regulation.
Other hormones, including GIP and glucagon, participate in energy balance through different mechanisms.
This distinction forms the foundation of the comparison between Semaglutide, Tirzepatide, and Retatrutide.
What Is Semaglutide?
Semaglutide is a GLP-1 receptor agonist used in FDA-approved prescription medications, including Ozempic and Wegovy.
It primarily targets the GLP-1 receptor.
Through this pathway, Semaglutide can influence appetite, fullness, gastric emptying, and glucose-dependent insulin signaling.
Semaglutide Clinical Research
A major clinical trial published in The New England Journal of Medicine in 2021 investigated once-weekly Semaglutide in adults with overweight or obesity without diabetes.
Known as the STEP 1 trial, the study enrolled 1,961 participants.
After 68 weeks, the trial reported:
TreatmentAverage body-weight changeSemaglutide 2.4 mg−14.9%Placebo−2.4%
The study demonstrated substantial weight reduction alongside changes in several cardiometabolic risk factors.
Its findings helped establish GLP-1 receptor agonism as a significant approach to obesity treatment.
View the STEP 1 Clinical Trial
What Is Tirzepatide?
Tirzepatide is a dual receptor agonist targeting:
GLP-1 — Glucagon-like peptide-1
GIP — Glucose-dependent insulinotropic polypeptide
GIP is another hormone involved in nutrient-responsive insulin secretion and metabolic signaling.
By activating both receptors, Tirzepatide influences two distinct but interacting metabolic pathways.
The compound is used in FDA-approved prescription medications including Mounjaro and Zepbound.
Why GIP Matters
GIP signaling contributes to glucose-dependent insulin release and additional processes involved in metabolism.
The interaction between GLP-1 and GIP receptors has attracted scientific interest because their combined activation can influence appetite, glucose regulation, and body weight.
However, receptor count alone does not determine clinical effectiveness.
The intensity, duration, and balance of receptor activity also matter.
Tirzepatide Clinical Research
The SURMOUNT-1 trial, published in The New England Journal of Medicine in 2022, investigated Tirzepatide in 2,539 adults with obesity or overweight and a weight-related complication, excluding diabetes.
After 72 weeks, the study reported:
TreatmentAverage body-weight changeTirzepatide 5 mg−15.0%Tirzepatide 10 mg−19.5%Tirzepatide 15 mg−20.9%Placebo−3.1%
The trial demonstrated substantial weight reduction through dual GLP-1 and GIP receptor agonism.
Researchers also observed improvements in several metabolic measurements.
View the SURMOUNT-1 Clinical Trial
What Makes Retatrutide Different?
Retatrutide, also known as LY3437943, is an investigational triple receptor agonist developed by Eli Lilly.
It activates three hormone receptors:
GLP-1
GIP
Glucagon
The additional glucagon receptor activity distinguishes Retatrutide from Semaglutide and Tirzepatide.
Glucagon is a hormone involved in hepatic glucose regulation, nutrient availability, and energy metabolism.
Its activity creates an additional area of investigation beyond GLP-1 and GIP signaling.
Why Glucagon Receptor Activity Is Interesting
Glucagon signaling influences how the liver processes and releases energy.
Its activation can affect glucose production, fatty acid metabolism, and energy expenditure.
Because glucagon can also increase blood glucose under certain circumstances, its activity must be understood in the context of the other receptors activated by Retatrutide.
The broader scientific concept is that different hormonal pathways may have interacting effects on metabolic regulation.
However, the addition of a third receptor does not automatically prove that a compound is better or safer than a dual or single receptor agonist.
Those outcomes require clinical investigation.
Retatrutide Phase 2 and Phase 3 Research
A 2023 Phase 2 trial published in The New England Journal of Medicine investigated Retatrutide in adults with obesity or overweight.
After 48 weeks, the highest studied dose group demonstrated an average body-weight reduction of 24.2%.
The findings generated considerable scientific interest in triple receptor activation.
Retatrutide TRIUMPH-1 Results
In May 2026, Eli Lilly announced results from its Phase 3 TRIUMPH-1 trial.
The study examined Retatrutide in adults with obesity or overweight and at least one weight-related comorbidity, without diabetes.
The reported efficacy analysis showed:
Retatrutide groupAverage weight reduction at 80 weeks4 mg19.0%9 mg25.9%12 mg28.3%
The 12 mg group experienced an average reduction of approximately 70 pounds.
Lilly also reported improvements in several metabolic and cardiovascular risk markers, including waist circumference, triglycerides, non-HDL cholesterol, and systolic blood pressure.
These findings represent trial-group averages, not guaranteed individual outcomes.
View Retatrutide Phase 3 Findings
Comparing Published Weight-Loss Results
The three compounds have produced substantial weight reductions in clinical research.
CompoundStudyDurationReported weight reductionSemaglutide 2.4 mgSTEP 168 weeks14.9%Tirzepatide 15 mgSURMOUNT-172 weeks20.9%Retatrutide 12 mgTRIUMPH-180 weeks28.3%
These results come from separate clinical trials and should not be interpreted as a direct head-to-head comparison.
The trials differed in treatment duration, participant characteristics, study design, and statistical analysis.
In particular, the Retatrutide figure is from an efficacy analysis, whereas the Semaglutide and Tirzepatide figures shown here use treatment-policy or treatment-regimen estimands.
Consequently, the percentages cannot establish the precise relative effectiveness of the three medications.
Direct randomized comparison trials provide stronger evidence for determining whether one treatment outperforms another.
Why Receptor Count Is Not the Whole Story
It is tempting to assume that activating three receptors must automatically outperform activating two, and that two must always outperform one.
The biology is more complicated.
A compound's effects depend on several factors:
Receptor-binding characteristics
Relative potency at each receptor
Duration of receptor activation
Pharmacokinetics
Tissue-specific responses
Tolerability
Treatment adherence
Individual metabolic characteristics
Two compounds targeting the same receptor may produce different clinical outcomes because of differences in molecular structure and biological activity.
Likewise, activating an additional receptor may introduce new physiological effects and safety considerations.
The number of receptors is therefore useful for describing a mechanism, but not sufficient for establishing superiority.
Appetite Regulation Versus Energy Expenditure
One of the most interesting distinctions in this research involves the relationship between food intake and energy expenditure.
GLP-1 and Appetite
GLP-1 receptor agonism influences satiety and food-related signaling.
These effects can reduce energy intake.
GIP and Metabolic Signaling
GIP participates in glucose-dependent insulin secretion and other aspects of energy regulation.
Its contribution depends on interactions with other hormonal systems.
Glucagon and Energy Regulation
Glucagon influences hepatic metabolism and energy availability.
Its activity is relevant to the investigation of energy expenditure and nutrient utilization.
This creates a broader research framework for Retatrutide, but it does not mean that every observed weight-loss effect comes directly from increased calorie burning.
The relative contribution of appetite changes and energy expenditure requires direct measurement.
What About Body Composition and Muscle Mass?
Body-weight reduction does not consist exclusively of fat loss.
Changes may involve fat mass, lean tissue, water, and other components.
Researchers increasingly examine body composition alongside total weight.
This is important because skeletal muscle contributes to physical function and glucose metabolism.
However, reductions in waist circumference do not directly quantify visceral fat, and total lean-mass measurements do not precisely measure skeletal muscle function.
Claims that one of these compounds guarantees muscle preservation or causes exclusively fat-based weight loss are not supported by the trials discussed here.
Safety and Tolerability Differences
The three compounds affect metabolic hormone systems and can produce adverse effects.
Commonly reported gastrointestinal effects include nausea, vomiting, diarrhea, and constipation.
Tolerability may differ by compound, treatment regimen, and individual characteristics.
Semaglutide and Tirzepatide have FDA-approved formulations with established prescribing information.
Retatrutide remains investigational as of October 2026.
Its clinical research has also identified increases in heart rate and other safety findings requiring continued evaluation.
Differences in adverse-event rates across separate trials should not be interpreted as proof that one compound is safer without appropriate comparative evidence.
Frequently Asked Questions
Is Retatrutide a GLP-1 Peptide?
Retatrutide activates the GLP-1 receptor, but it also activates GIP and glucagon receptors. It is therefore more precisely described as a triple receptor agonist.
Is Tirzepatide the Same as Semaglutide?
No. Semaglutide activates GLP-1 receptors, while Tirzepatide activates GLP-1 and GIP receptors.
What Is the Main Difference Between Tirzepatide and Retatrutide?
Retatrutide adds glucagon receptor activity to GLP-1 and GIP signaling.
Which Compound Produced the Greatest Reported Weight Reduction?
Among the specific trials discussed here, Retatrutide's TRIUMPH-1 study reported the largest numerical average reduction. However, the trials are not directly comparable, and this does not establish head-to-head superiority.
Is Retatrutide FDA-Approved?
Retatrutide remains investigational as of October 2026 and has not received FDA approval.
Do More Hormone Receptors Mean Better Results?
Not necessarily. Clinical results depend on receptor activity, study conditions, safety, and numerous other factors.
Final Thoughts
Semaglutide, Tirzepatide, and Retatrutide represent three different approaches to metabolic hormone research.
Semaglutide investigates GLP-1 receptor activation.
Tirzepatide combines GLP-1 and GIP receptor signaling.
Retatrutide adds glucagon receptor activity, expanding the range of metabolic pathways under investigation.
Each has contributed important findings to the scientific understanding of appetite, body weight, glucose regulation, and energy balance.
The most meaningful comparisons require examining receptor mechanisms, study design, clinical outcomes, and safety rather than simply counting the number of receptors involved.
Published Research and References
Wilding JPH, et al. (2021). Once-Weekly Semaglutide in Adults with Overweight or Obesity. New England Journal of Medicine.
Jastreboff AM, et al. (2022). Tirzepatide Once Weekly for the Treatment of Obesity. New England Journal of Medicine.
Jastreboff AM, et al. (2023). Triple–Hormone-Receptor Agonist Retatrutide for Obesity — A Phase 2 Trial. New England Journal of Medicine.
Eli Lilly and Company (2026). TRIUMPH-1 Phase 3 Retatrutide Results.
Research Disclaimer: This article is provided by DeSoto Peptides for educational purposes only. Retatrutide is investigational and not FDA-approved. Semaglutide and Tirzepatide have approved prescription formulations for specific indications. This article does not recommend obtaining or administering unapproved compounds and does not constitute medical advice.