Keel
Growth Hormone

Ipamorelin

Ipamorelin is a small peptide studied for its ability to prompt the pituitary gland to release growth hormone. It's particularly well known in the research literature for doing this selectively, without meaningfully raising other hormones like cortisol that similar compounds tend to affect.

Sequence
5 amino acids
Format
Lyophilized powder
Half-Life
Approximately 2 hours

What Is Ipamorelin?

Ipamorelin is a synthetic pentapeptide, meaning it's built from a chain of five amino acids, developed as part of a broader effort to find growth hormone secretagogues, compounds that trigger the pituitary gland to release growth hormone. It works through the same receptor as ghrelin, the body's natural hunger hormone, which is why it's classified in the ghrelin receptor agonist family.

What set ipamorelin apart when it was first characterized was its selectivity. Earlier compounds in its class tended to raise other hormones like cortisol and prolactin along with growth hormone, but research found ipamorelin stimulated growth hormone release without those side effects at comparable doses.[1]

What Ipamorelin Is Being Researched For

  • Selective Growth Hormone Release

    The defining area of ipamorelin research is its ability to stimulate growth hormone release while leaving other pituitary hormones, including cortisol, prolactin, and ACTH, largely unaffected.[1]

  • Pharmacokinetics and Dosing Patterns

    A dedicated human trial characterized how ipamorelin behaves in the body over time, mapping out its absorption, clearance, and the timing of the growth hormone response it triggers.[2]

  • Comparative Research Within Its Drug Class

    Because ipamorelin sits alongside other growth hormone secretagogues developed over several decades, researchers have reviewed how it compares mechanistically and in selectivity to earlier compounds in the same family.[3]

How Ipamorelin Works

  • Activating the Ghrelin Receptor

    Research points to ipamorelin binding to the growth hormone secretagogue receptor, the same receptor ghrelin naturally activates, which triggers a signaling cascade in the pituitary gland leading to growth hormone release.[1]

  • A Single, Time-Limited Release Pattern

    Research points to ipamorelin producing one distinct pulse of growth hormone release rather than a sustained elevation. Human studies found the growth hormone response peaked around 40 minutes after administration and then declined, mirroring the body's own natural pulsatile release pattern.[2]

  • Avoiding Broader Hormonal Effects

    Research points to ipamorelin's structure allowing it to trigger growth hormone release through the ghrelin receptor pathway without significantly activating the signaling that raises cortisol and prolactin in related compounds, which is the basis for its reputation as a more selective option in its class.[1]

Reconstitution and Handling

Ipamorelin is typically supplied as a lyophilized powder in a sealed vial and reconstituted with bacteriostatic water before use in a research setting. Water should be added slowly rather than injected directly into the powder, and the vial should be swirled, not shaken.

Since the amount of water used affects the concentration of the final solution, researchers often use a dosage calculator to work this out before mixing. Once reconstituted, the solution is kept refrigerated to help preserve its stability.

Key Takeaways

Ipamorelin's defining feature in the research literature is selectivity, triggering growth hormone release through the ghrelin receptor pathway without the broader hormonal effects seen in earlier compounds in its class. Its research base includes both the original selectivity findings and a dedicated human pharmacokinetic study mapping its behavior over time. It remains a research compound without an approved therapeutic indication.

Clinical Overview

Evidence Summary

  • Human

    A dedicated pharmacokinetic-pharmacodynamic study in healthy human volunteers characterized the growth hormone response to single intravenous doses of ipamorelin, establishing dose-dependent GH release in humans.[2]

  • Animal

    In the original characterization studies, ipamorelin stimulated growth hormone release in rats and swine with a potency comparable to GHRP-6 but without the concurrent rise in ACTH, cortisol, or prolactin seen with other secretagogues.[1]

  • RCT

    Ipamorelin advanced to a completed randomized clinical trial for postoperative ileus, but the development program did not demonstrate efficacy sufficient for approval, and it has no approved therapeutic indication.[3][4]

  • In vitro

    Mechanistic work confirms ipamorelin acts as an agonist at the growth hormone secretagogue receptor (ghrelin receptor), the pathway that mediates its selective GH-releasing effect.[1][3]

Pharmacokinetics

  • Route

    Ipamorelin has no approved formulation; human pharmacokinetic data derive from intravenous dosing in research settings, and subcutaneous administration is the common non-clinical route.[2]

  • Half-Life

    The elimination half-life in human volunteers was reported at approximately 2 hours following intravenous administration.[2]

  • Time to Peak Effect

    The stimulated growth hormone response peaks roughly 40 minutes after administration and then declines, producing a single discrete pulse rather than sustained elevation.[2]

  • Metabolism and Clearance

    As a small pentapeptide, ipamorelin is presumed to undergo proteolytic degradation; detailed human metabolism and clearance-pathway data are not established in the published literature.[2]

Contraindications and Interactions

  • Investigational compound with no approved human indication; not established as safe or effective for any therapeutic use.[3]
  • No published human data address safety in pregnancy or lactation.
  • Growth hormone and IGF-1 elevation is theoretically undesirable in the setting of neoplasia; no human data address use in patients with active or prior malignancy.
  • Growth hormone secretagogues can reduce insulin sensitivity, a theoretical concern in patients with diabetes or impaired glucose tolerance.[3]
  • As a ghrelin receptor agonist, additive effects with other growth hormone secretagogues or with drugs affecting gastric motility are theoretically possible.[3]

Monitoring Parameters

  • Clinicians commonly track IGF-1 as a marker of cumulative growth hormone axis stimulation.
  • Fasting glucose and HbA1c are commonly tracked given the potential for reduced insulin sensitivity with GH-axis stimulation.
  • Symptoms of fluid retention, including peripheral edema, arthralgia, and carpal tunnel-type complaints, are relevant given the association with growth hormone excess.
  • Cortisol and prolactin were reported to be largely unaffected in characterization studies, so reassessment is relevant mainly if unexpected endocrine symptoms arise.[1]

Reported Adverse Events

  • Injection-site reactions are plausible with parenteral use.
  • Headache and transient flushing.
  • Fluid retention, arthralgia, and paresthesias attributable to growth hormone axis stimulation.
  • Transient increases in appetite consistent with ghrelin receptor agonism.[1]

Frequently Asked Questions

What Is Ipamorelin Derived From?

It's a synthetic peptide developed from an earlier growth hormone-releasing peptide sequence, refined specifically for greater selectivity.

What Has Ipamorelin Been Studied For?

Research has focused mainly on its selective growth hormone-releasing effect, along with detailed human pharmacokinetic studies mapping how it behaves in the body.

How Is Ipamorelin Different from Other Growth Hormone Secretagogues?

Its main distinction is selectivity. Studies have found it raises growth hormone without meaningfully increasing cortisol, prolactin, or ACTH, unlike some earlier compounds in its class.

Has Ipamorelin Been Tested in Humans?

Yes, in pharmacokinetic and pharmacodynamic studies characterizing how it behaves in the body. It also underwent a completed clinical trial for a gastrointestinal condition, though that development program did not lead to approval.

Sources and Research

  1. Raun K, Hansen BS, Johansen NL, et al. Ipamorelin, the first selective growth hormone secretagogue. Eur J Endocrinol. 1998;139(5):552-561.
  2. Gobburu JVS, Agersø H, Jusko WJ, Ynddal L. Pharmacokinetic-Pharmacodynamic Modeling of Ipamorelin, a Growth Hormone Releasing Peptide, in Human Volunteers. Pharm Res. 1999;16(9):1412-1416.
  3. Ishida J, Saitoh M, Ebner N, Springer J, Anker SD, von Haehling S. Growth hormone secretagogues: history, mechanism of action, and clinical development. JCSM Rapid Commun. 2020;3(1):25-37.
  4. Beck DE, Sweeney WB, McCarter MD; Ipamorelin 201 Study Group. Prospective, randomized, controlled, proof-of-concept study of the Ghrelin mimetic ipamorelin for the management of postoperative ileus in bowel resection patients. Int J Colorectal Dis. 2014;29(12):1527-1534.

Related Reading

For educational and research purposes only. Not medical advice. Always consult a licensed healthcare professional before starting any protocol.