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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.
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.