Receptors are proteins that wait for a specific signal, such as a hormone or a neurotransmitter, to trigger a response inside the cell. An agonist is any molecule able to occupy that receptor and switch it on. The natural hormone is the endogenous agonist; many research peptides are synthetic agonists designed to last longer or to be more selective.
Not all agonists switch the receptor on with the same intensity. A full agonist produces the maximum possible response; a partial agonist produces only a fraction of it, even when it occupies every receptor. Some agonists also favour certain signalling pathways over others within the same receptor, a phenomenon called biased agonism.
Semaglutide is an agonist of the GLP-1 receptor; ipamorelin, of the ghrelin receptor (GHS-R1a); tirzepatide is an agonist of two receptors at once and retatrutide of three.
Knowing which receptor a compound is an agonist of is the fastest way to understand what it is studied for, which compounds it is compared with and which class effects to expect in experimental models.
Related terms
Learn it in depth at the Peptide University
- Metabolic and repair (1–5) · Module 14
- Pharmacodynamics: receptors and signaling · Module 2
- G protein-coupled receptors: desensitization and tolerance · Module 2
- Somatotropic, neuro and others (11–15) · Module 14
- Levels of structure and structure-activity relationship · Module 1
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Definition for educational and scientific purposes. It is not medical advice or a recommendation for use. NeoPeptidos products are sold labelled for research use only (RUO).