Ghrelin Mimetics: Ipamorelin, GHRP-2, GHRP-6, Hexarelin
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Ghrelin mimetics stimulate growth hormone release through the ghrelin receptor (GHS-R1a). A few are approved for narrow uses, such as macimorelin as an oral diagnostic test in the US and anamorelin for cancer cachexia in Japan. Ipamorelin, GHRP-6 and hexarelin have no approval, and all GH secretagogues are prohibited in sport. Vegalab does not make, sell or source them.
Mechanism
Ghrelin is a 28-amino-acid acylated stomach peptide that binds GHS-R1a in the pituitary and hypothalamus, releasing GH and increasing appetite. Growth hormone-releasing peptides (GHRPs) were developed before ghrelin was discovered. GHRP-6 and hexarelin are hexapeptides; GHRP-2 (pralmorelin) is a shorter analog. Ipamorelin is a pentapeptide selected for GH release without the cortisol and prolactin increases seen with GHRP-6 in animal studies. Ghrelin mimetics can also increase appetite and blood glucose, which limits their use.
Regulatory status
Macimorelin (Macrilen), an orally active small-molecule ghrelin agonist, is FDA-approved as a diagnostic for adult GH deficiency. Anamorelin (Adlumiz) is approved in Japan for cancer cachexia. GHRP-2 (pralmorelin) is used in Japan as a diagnostic agent. Ipamorelin reached phase 2 for postoperative ileus and was not approved. GHRP-6 and hexarelin have no approvals. WADA S2 prohibits growth hormone secretagogues and GHRPs, naming these compounds. Clinicians asked about these peptides should refer to approved therapies.
Delivery profile
The peptide GHRPs have short half-lives, typically around two hours for ipamorelin, and are given by injection in research settings. Macimorelin shows that oral delivery is achievable for a ghrelin agonist when the molecule is designed as a peptidomimetic from the start rather than a native peptide. Oral activity of small-molecule agonists like macimorelin and anamorelin comes from drug-like structures that resist proteases and cross membranes. Native peptide GHRPs lack these properties.
Why this page exists
GH secretagogues are common in gray-market peptide stacks. This page separates approved diagnostic and cachexia agents from unapproved research peptides. Clinicians and athletes ask about these compounds often. The key distinction is between approved agents with narrow uses and unapproved peptides sold as research chemicals, which vary in quality and carry sanctions for athletes. Formulation work is appropriate only with approved molecules and their license holders. Vegalab does not formulate unapproved GHRPs.
Key facts
- Ipamorelin was characterized as a selective GH secretagogue without significant ACTH or cortisol release in animals (Raun et al. 1998, Eur J Endocrinol 139:552)
- Macimorelin is FDA-approved as an oral test for diagnosing adult growth hormone deficiency (FDA label, Macrilen 2017)
- Anamorelin was approved in Japan for cancer cachexia (Wakabayashi et al. 2021, J Cachexia Sarcopenia Muscle 12:14)
- Growth hormone secretagogues and GHRPs, e.g. ipamorelin, GHRP-2, GHRP-6 and hexarelin, are prohibited under S2 (WADA Prohibited List 2026)
How our delivery technology applies
Macimorelin and anamorelin show that the path to oral ghrelin agonism has been medicinal chemistry, not encapsulation of peptides. Where encapsulation adds value is for approved molecules with dosing or palatability issues, for example taste masking and controlled release of an oral agent. We would take on that work only for approved products with their license holders, and not for unapproved GHRPs.
Holders of approved oral agents: explore taste-masked, controlled-release formats with Vegalab.