Substance class
GHRP
4 entries
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Ipamorelin
NNC 26-0161
Ipamorelin is a synthetic pentapeptide and a selective agonist at the ghrelin receptor (GHS-R1a). By binding to this receptor in the pituitary and hypothalamus, it stimulates the pulsatile secretion of growth hormone (GH). Compared with other GHRP compounds (e.g. GHRP-6), ipamorelin shows lower stimulation of ACTH and cortisol in preclinical studies, which has been regarded as a potential selectivity advantage — clinical confirmation is pending.
GHRP-2
Pralmorelin
GHRP-2 is a synthetic hexapeptide that acts as a potent agonist at the ghrelin receptor (GHS-R1a). Binding to GHS-R1a in the somatotroph cells of the anterior pituitary triggers a strong pulsatile release of growth hormone (GH). At the same time, its hypothalamic action reduces somatostatin inhibition, further amplifying the GH pulse. Compared with GHRP-6, GHRP-2 stimulates appetite less markedly, as its ghrelinergic action on the hypothalamus is weaker. GHRP-2 also moderately raises prolactin and cortisol — an effect that can be clinically relevant at therapeutic doses.
GHRP-6
Growth Hormone Releasing Peptide-6
GHRP-6 is the first synthetic growth hormone secretagogue (GHS) and the prototype of the GHRP class. As a potent GHS-R1a agonist, it triggers pulsatile GH release from the pituitary. Characteristic of GHRP-6 is a pronounced ghrelin-mimetic effect in the hypothalamus, which, alongside GH release, mediates strong appetite stimulation via NPY and AgRP neurons. This appetite effect clinically distinguishes GHRP-6 from more selective GHRPs such as ipamorelin. GHRP-6 also raises cortisol and prolactin, more strongly than GHRP-2.
Hexarelin
Examorelin
Hexarelin is a synthetic hexapeptide and the most potent GH secretagogue of the GHRP class. As a high-affinity GHS-R1a agonist, at equimolar doses it produces 2–3-fold higher GH pulses than GHRP-2, GHRP-6 or ipamorelin. In addition to GHS-R1a activity, hexarelin binds the CD36 scavenger receptor — a mechanism shown by no other GHRP compound and thought to mediate cardioprotective effects (reduction of myocardial fibrosis, improved cardiac function in animal models). Hexarelin raises cortisol and prolactin more strongly than other GHRPs and shows pronounced tachyphylaxis.