Glossary
GHRP
GHRPs are synthetic agonists of the ghrelin receptor that cause pituitary GH release. How GHRP-2, GHRP-6, ipamorelin and hexarelin compare with each other.
GHRPs, or growth hormone-releasing peptides, are short synthetic peptides that cause the pituitary to release growth hormone by acting on the ghrelin receptor, GHS-R1a, rather than on the GHRH receptor. They are older than the discovery of ghrelin: GHRP-6 emerged from opioid-peptide chemistry during the 1970s and 1980s, while the natural ligand of its receptor was only identified in 1999.
Comparing the family members
The members are distinguished mainly by selectivity. GHRP-6, a hexapeptide, is reported to stimulate appetite strongly via ghrelin-receptor signalling. GHRP-2 releases GH more potently and affects appetite less, although some rise in cortisol and prolactin has been reported. Ipamorelin, a pentapeptide, was chosen for its selectivity and shows little reported cortisol or prolactin response. Hexarelin is the most potent in acute settings but, in published studies, desensitises its receptor fastest.
Choosing between them
Each of the four is a growth hormone secretagogue, yet they cannot stand in for one another as comparators. Which one suits a particular research question usually depends on its selectivity profile rather than on its raw potency.
Related terms
GHRH. Browse GHRPs and secretagogues or compare in Ipamorelin vs GHRP-2.