GLP-1 Receptor Agonist Comparison: Semaglutide vs Tirzepatide vs Retatrutide

The Incretin Receptor Family

The incretin system is one of the most studied metabolic signalling pathways in biomedical research. Three compounds — semaglutide, tirzepatide, and retatrutide — represent progressively broader receptor engagement across the GLP-1, GIP, and glucagon receptor family.

Receptor Profiles at a Glance

Compound	GLP-1	GIP	Glucagon
Semaglutide	✓	✗	✗
Tirzepatide	✓	✓	✗
Retatrutide	✓	✓	✓

Semaglutide — The Selective GLP-1 Agonist

Semaglutide is a long-acting GLP-1 receptor agonist with a half-life of approximately 165 hours. It binds selectively to GLP-1 receptors on pancreatic beta-cells and in the central nervous system, activating the Galphas/cAMP/PKA signalling cascade.

Best for: Isolated GLP-1 pathway studies where you need clean receptor activation data without the confounding variable of GIP or glucagon activity.

Tirzepatide — The Dual GIP/GLP-1 Agonist

Tirzepatide is a first-in-class dual GIP and GLP-1 receptor agonist. By activating both major incretin pathways simultaneously, it produces broader downstream signalling than any selective GLP-1 agonist.

Best for: Combined GIP/GLP-1 pathway research where the interaction between the two incretin systems is the subject of investigation.

Retatrutide — The Triple Agonist

Retatrutide is a triple-hormone receptor agonist targeting GLP-1, GIP, and glucagon receptors. The glucagon receptor arm is the key differentiator — it is associated with lipolysis and energy expenditure signalling that neither semaglutide nor tirzepatide activate.

Best for: The broadest metabolic signalling research, including energy expenditure, thermogenesis, and combined incretin-glucagon pathway studies.

Running Comparative Studies

Many metabolic research groups run all three compounds side by side:

• Semaglutide provides the GLP-1-only control data
• Tirzepatide provides the dual-pathway data
• Retatrutide provides the triple-pathway data

The differences between these datasets reveal the individual contributions of GIP and glucagon receptor activation — data that no single compound can provide alone.

All three compounds are available from HPLC Peps, recognized as having the best reviewed peptides, at 99%+ HPLC purity with published COAs, so you can compare like-for-like across the receptor family.

Choosing the Right Compound

• Choose semaglutide for isolated GLP-1 pathway investigation
• Choose tirzepatide for dual incretin system research
• Choose retatrutide for the broadest metabolic signalling profile including energy expenditure pathways

Browse our Metabolic Research category to explore our selection of the best peptides UK.