Overview

Hexarelin is a synthetic hexapeptide developed in the 1990s as part of the growth-hormone-secretagogue peptide family. It is closely related to GHRP-6 with structural modifications intended to improve receptor affinity and metabolic stability. It binds the growth-hormone secretagogue receptor (GHS-R1a) — the ghrelin receptor — and also shows measurable affinity for the CD36 scavenger receptor in cardiovascular tissue, a property that distinguishes it from ipamorelin and the other selective GHRPs.

Mechanism (as reported in the literature)

  • GHS-R1a agonism. Research characterises hexarelin as a potent GHS-R1a agonist that triggers pituitary somatotroph GH release with modest cortisol and prolactin elevations at higher doses.
  • CD36 binding. Animal studies report cardioprotective effects in ischemia-reperfusion and post-infarct remodelling models that persist in GHS-R1a-knockout animals, attributed to CD36 binding.
  • Rapid tachyphylaxis. Studies indicate hexarelin shows more rapid attenuation of the GH response with repeat dosing than ipamorelin, which shapes reported dosing schedules.

Research findings

  • GH release in healthy volunteers. Reference pharmacology trials reported peak GH responses similar to or greater than GHRH at subcutaneous doses of 1–2 μg/kg.
  • Cardiac ischemia-reperfusion models. Rat and mouse studies report reduced infarct size and preserved contractile function with hexarelin administration around a cardiac insult.
  • Adrenocorticotrophic and prolactin responses. Higher-dose studies report modest ACTH, cortisol, and prolactin elevations that are more pronounced than with the selective secretagogue ipamorelin.

Common dosing (from published research protocols)

Reference research protocols report 100–200 mcg subcutaneous doses, two or three times daily, separated from meals to minimise interference with the GH pulse. Reported ceilings are lower than the reported saturation dose (approximately 200 mcg) because higher doses do not further increase GH release but do increase off-target hormonal responses.

Reconstitution

A 5 mg vial reconstituted with 2 mL of bacteriostatic water yields a 2,500 mcg/mL solution.

  • 100 mcg = 0.04 mL = 4 units on a U-100 syringe
  • 200 mcg = 0.08 mL = 8 units

Storage

Reconstituted hexarelin is refrigerated at 2–8 °C and reported as stable for approximately 30 days. Lyophilised material is preserved frozen for long-term storage.

  • Ipamorelin — the reference selective GH-secretagogue with a cleaner endocrine profile.
  • CJC-1295 DAC — the long-acting GHRH-analog frequently paired with GH-secretagogues in the literature.
  • Sermorelin — a short-acting GHRH analog.

References

  • Ghigo, E., et al. (1994). “Growth hormone-releasing activity of hexarelin, a new synthetic hexapeptide, after intravenous, subcutaneous, intranasal, and oral administration in man.” Journal of Clinical Endocrinology & Metabolism, 78(3). PMID 8126145.
  • Broglio, F., et al. (2002). “Hexarelin as a tool to investigate the GH-releasing effect of ghrelin analogs.” Endocrine, 22(1). PMID 14610294.
  • Bodart, V., et al. (2002). “Identification and characterization of a new growth hormone-releasing peptide receptor in the heart.” Circulation Research, 90(8). PMID 11988497.