Summary

Hexarelin is a synthetic hexapeptide belonging to the growth hormone-releasing peptide (GHRP) family. It acts on the ghrelin receptor (GHS-R1a) to stimulate growth hormone release from the pituitary gland. Research suggests it is among the most potent GHRPs, with additional interest in its cardioprotective effects independent of GH release. Evidence comes primarily from animal models and a limited number of human studies.

Mechanism

Hexarelin is a ghrelin receptor (GHS-R1a) agonist. Binding to the ghrelin receptor on somatotroph cells in the anterior pituitary triggers a signalling cascade (via Gq/11 and phospholipase C) that stimulates growth hormone release. Unlike GHRH analogues, this pathway is not subject to somatostatin inhibition to the same degree. Hexarelin also appears to bind to specific cardiac receptors (including CD36) that may mediate its GH-independent cardioprotective effects.

Evidence base

Hexarelin has been studied in human pharmacological trials demonstrating potent GH-releasing activity (Rahim et al., 1995; Deghenghi et al., 1994). The cardioprotective effects are well-documented in animal models, including in hypophysectomised rats confirming GH-independence (Locatelli et al., 1999; Bodart et al., 2002), but human clinical evidence for cardiac benefits remains limited. Overall evidence is graded as moderate — robust for GH-releasing effects in humans, but preclinical for cardioprotection.

Protocols

In published human studies, hexarelin has been administered intravenously at 0.5–2.0 µg/kg and subcutaneously at approximately 1–2 µg/kg (Rahim et al., 1995). It is commonly discussed in research contexts alongside a GHRH analogue for synergistic GH release. Cycle lengths of 4–8 weeks are commonly referenced. These are research protocols, not medical dosing instructions.

Hexarelin is not a UK-licensed medicine and is not a controlled substance. It falls into a grey area — legal to purchase and possess for research purposes, but not approved by the MHRA for human therapeutic use. Should be sold for research purposes only.

Vendor notes

No UK vendors have been independently verified for hexarelin at this time. Researchers should follow the guidance in our Vendor Vetting Guide when evaluating suppliers.

References

  1. Rahim A, Toogood AA, Shalet SM. The effect of varying subcutaneous doses of hexarelin on growth hormone, prolactin and cortisol release in normal human volunteers. Journal of Endocrinology. 1995;147(1):147-152.
  2. Deghenghi R, Cananzi MM, Torsello A, et al. GH-releasing activity of hexarelin, a new growth hormone releasing peptide, in normal subjects and in elderly subjects. Journal of Endocrinological Investigation. 1994;17(8):639-642.
  3. Locatelli V, Grilli R, Torsello A, et al. Growth hormone-releasing peptides: a study on hexarelin in rats. Journal of Endocrinology. 1999;161(1):S5-S13.
  4. Bodart V, Bouchard P, McNicoll N, et al. Identification and characterization of a new growth hormone-releasing peptide receptor in the heart. Circulation Research. 2002;85(8):796-802.
  5. Raun K, Hansen BS, Johansen NL, et al. Ipamorelin, the first selective growth hormone secretagogue. European Journal of Endocrinology. 1998;139(5):552-561.
  6. Mao Y, Liu Z, Liang R, et al. Hexarelin attenuates cardiac fibrosis in rats. Cardiovascular Drugs and Therapy. 2022;36(1):39-50.