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Research Only Growth Hormone Axis

Ghrelin

also known as: Lenomorelin, Growth Hormone Releasing Peptide, Hunger Hormone

The 'hunger hormone' — the only known circulating appetite stimulant, and the endogenous ligand that GHRP-2, GHRP-6, and MK-677 were designed to mimic.

A 28-amino-acid acylated peptide hormone discovered in 1999, secreted by the stomach, that stimulates appetite, GH release, and energy storage via the GHS-R1a receptor.

Mechanism of action

Binds GHS-R1a (a constitutively active GPCR) to stimulate GH release from the anterior pituitary, increase appetite via hypothalamic NPY/AgRP neurons, modulate gastric motility, and influence glucose homeostasis. The unique octanoyl modification on Ser3 (catalyzed by GOAT enzyme) is required for GHS-R1a activation.

Primary uses

  • Appetite and GH secretion research
  • Cachexia and anorexia research tool
  • Metabolic physiology studies
  • Gastrointestinal motility research

Typical dosing

1–5 mcg/kg IV infusion (research only) (intravenous)

Used in clinical research protocols only. No established therapeutic dosing.

Regulatory status

Not approved as a therapeutic. Synthetic ghrelin infusions used in clinical research settings. Ghrelin agonists (anamorelin, macimorelin) are separate approved/investigational agents.

References

  1. [pubmed] Kojima M, et al. "Ghrelin is a growth-hormone-releasing acylated peptide from stomach." Nature, 1999;402:656-660.
  2. [review] Müller TD, et al. "Ghrelin." Mol Metab, 2015;4:437-460.

Related peptides

MK-677

An orally active non-peptide ghrelin receptor agonist — included here by convention because it is universally marketed alongside peptide GH secretagogues. FDA warns of heart failure risk.

GHRP-2

A second-generation GHRP approved as a diagnostic agent in Japan, with more pronounced GH-releasing potency than GHRP-6 but a meaningful prolactin and cortisol rise at higher doses.

GHRP-6

The prototype GHRP — a hexapeptide ghrelin receptor agonist notable for pronounced hunger stimulation and less favorable cortisol/prolactin profile than newer GHRPs.

Hexarelin

A high-potency GHRP studied for cardiac protection via a CD36-mediated pathway independent of GH release — but demonstrates clear tachyphylaxis with chronic use.

Anamorelin

Ono Pharmaceutical's oral ghrelin receptor agonist (Adlumiz) — approved in Japan in 2021 for cancer cachexia in non-small-cell lung, gastric, pancreatic, and colorectal cancers; FDA issued a Complete Response Letter in 2020 and anamorelin remains unapproved in the US.

Guides & tools

Disclaimer

This entry is for educational purposes only and does not constitute medical advice. Dosing information reflects published regulatory or research data and is not a recommendation. Many compounds described here are not approved for human use in the United States. Consult a licensed medical professional before considering any peptide therapy.