Mechanism of action

Hexarelin supplies a stimulus for endogenous GH release, whereas the full GH protein is a different substance. Imbimbo and colleagues used placebo comparisons to examine a rising GH response, and Ghigo and colleagues compared responses under different experimental routes and reference conditions. Korbonits et al. (1995) tested whether naloxone, an opioid-receptor blocker, altered the response. Naloxone did not prevent the GH-stimulating effect in that experiment. Prolactin, cortisol and ACTH increases were also recorded. These broader hormone measurements mean that an observed GH response should not be described as proof that the compound acts exclusively on GH secretion.

State of evidence

Imbimbo's 1994 double-blind placebo-controlled rising-exposure study involved 12 adult male volunteers. Ghigo's study examined 12 healthy young volunteers with saline and GHRH reference conditions while comparing different study routes. Korbonits' randomized double-blind experiment also involved 12 volunteers and focused on hormone responses and opioid blockade. Together, these papers support an experimental GH-releasing effect but do not measure sustained functional, recovery or aging outcomes. A separate peptide pharmacokinetic paper studied dogs, which cannot supply a human elimination constant. The preparation, route, population and measured molecule must remain visible when interpreting the work. Small physiological experiments also do not establish the quality or clinical suitability of an unrelated preparation.

Questions about the research

Is hexarelin a form of the growth hormone protein?

No. It is a short secretagogue peptide investigated as a stimulus for GH secretion. The stimulating peptide and the hormone released by the endocrine system have different identities. Their measurements and effects cannot be treated as interchangeable.

Do these experiments show improved strength or recovery?

The selected volunteer studies investigated hormone responses. A functional or recovery benefit requires a study designed to measure that outcome in an applicable population. A rise in circulating GH cannot substitute for such evidence.

Does a declining GH response measure hexarelin elimination?

No. GH concentration after stimulation and the concentration of hexarelin itself are separate measurements. The canine peptide study addresses another species. Neither a human GH-response curve nor an animal value supplies a universal human half-life for the peptide.

Sources

1. Imbimbo et al., Eur J Clin Pharmacol 1994DOI: 10.1007/BF00191904PMID: 7957536
2. Ghigo et al., J Clin Endocrinol Metab 1994DOI: 10.1210/jcem.78.3.8126144PMID: 8126144
3. Korbonits et al., Clin Endocrinol 1995DOI: 10.1111/j.1365-2265.1995.tb02045.xPMID: 7586608
4. Roumi et al., Peptides 1995, canine peptide pharmacokineticsDOI: 10.1016/0196-9781(95)02022-oPMID: 8545255

Mechanism of action

Hexarelin supplies a stimulus for endogenous GH release, whereas the full GH protein is a different substance. Imbimbo and colleagues used placebo comparisons to examine a rising GH response, and Ghigo and colleagues compared responses under different experimental routes and reference conditions. Korbonits et al. (1995) tested whether naloxone, an opioid-receptor blocker, altered the response. Naloxone did not prevent the GH-stimulating effect in that experiment. Prolactin, cortisol and ACTH increases were also recorded. These broader hormone measurements mean that an observed GH response should not be described as proof that the compound acts exclusively on GH secretion.

State of evidence

Imbimbo's 1994 double-blind placebo-controlled rising-exposure study involved 12 adult male volunteers. Ghigo's study examined 12 healthy young volunteers with saline and GHRH reference conditions while comparing different study routes. Korbonits' randomized double-blind experiment also involved 12 volunteers and focused on hormone responses and opioid blockade. Together, these papers support an experimental GH-releasing effect but do not measure sustained functional, recovery or aging outcomes. A separate peptide pharmacokinetic paper studied dogs, which cannot supply a human elimination constant. The preparation, route, population and measured molecule must remain visible when interpreting the work. Small physiological experiments also do not establish the quality or clinical suitability of an unrelated preparation.

Questions about the research

Is hexarelin a form of the growth hormone protein?

No. It is a short secretagogue peptide investigated as a stimulus for GH secretion. The stimulating peptide and the hormone released by the endocrine system have different identities. Their measurements and effects cannot be treated as interchangeable.

Do these experiments show improved strength or recovery?

The selected volunteer studies investigated hormone responses. A functional or recovery benefit requires a study designed to measure that outcome in an applicable population. A rise in circulating GH cannot substitute for such evidence.

Does a declining GH response measure hexarelin elimination?

No. GH concentration after stimulation and the concentration of hexarelin itself are separate measurements. The canine peptide study addresses another species. Neither a human GH-response curve nor an animal value supplies a universal human half-life for the peptide.

Sources

1. Imbimbo et al., Eur J Clin Pharmacol 1994DOI: 10.1007/BF00191904PMID: 7957536
2. Ghigo et al., J Clin Endocrinol Metab 1994DOI: 10.1210/jcem.78.3.8126144PMID: 8126144
3. Korbonits et al., Clin Endocrinol 1995DOI: 10.1111/j.1365-2265.1995.tb02045.xPMID: 7586608
4. Roumi et al., Peptides 1995, canine peptide pharmacokineticsDOI: 10.1016/0196-9781(95)02022-oPMID: 8545255