Peptide Health Lab

Growth hormone axis

Ipamorelin

FOR RESEARCH PURPOSES ONLY

Regulatory status
Research only
Evidence grade
Anecdotal reports only

Last reviewed August 2, 2026 · 12 sources

What ipamorelin is and how it works

Ipamorelin is a synthetic pentapeptide, Aib-His-D-2-Nal-D-Phe-Lys-NH2, developed at Novo Nordisk out of a chemistry programme built around growth-hormone-releasing peptide-1. Removing the central Ala-Trp dipeptide from that scaffold produced a series of compounds, and ipamorelin was the one selected from it.[1]

It is not a GHRH analog. It acts at the growth hormone secretagogue receptor, the receptor for ghrelin, which is a separate pathway from the GHRH receptor. Its mechanism was confirmed pharmacologically by showing that GHRP antagonists blocked its effect while GHRH antagonists did not.[1] Both pathways converge on the same pituitary somatotropes, which is why the two classes are often discussed together.

What made ipamorelin interesting to its developers was selectivity. Earlier compounds in the class, GHRP-6 and GHRP-2, raise ACTH and cortisol along with growth hormone. Ipamorelin, tested in conscious swine at doses more than 200-fold above its GH-releasing ED50, did not. It left FSH, LH, prolactin, and TSH unmoved as well. The authors described it as the first GHRP-receptor agonist with a selectivity for GH release comparable to GHRH itself.[1]

In humans, the pharmacology is short-acting: dose-proportional kinetics, a terminal half-life of about two hours, clearance of 0.078 L/h/kg, and a single episode of GH release peaking around 40 minutes after infusion and then declining to negligible concentrations.[3] That episodic profile, a pulse rather than a sustained elevation, is the mechanistic argument its proponents make. The argument is about shape, not about any demonstrated outcome.

What the research actually shows

The rodent literature is coherent and reasonably deep. In cultured rat pituitary cells ipamorelin released GH with potency and efficacy similar to GHRP-6, and the same held in anaesthetized rats and conscious swine.[1] In adult female rats dosed subcutaneously three times daily for 15 days, longitudinal bone growth rate rose dose-dependently from 42 µm/day in controls to 52 µm/day at the top dose, with a pronounced effect on body weight gain, although total IGF-1, IGF binding proteins, and serum markers of bone turnover were unchanged.[2] Over 12 weeks of continuous subcutaneous infusion, ipamorelin increased bone mineral content in young adult female rats.[4] In an adult rat model of glucocorticoid-induced catabolism, three months of ipamorelin alongside methylprednisolone increased maximum tetanic tension of the calf muscles and raised the periosteal bone formation rate fourfold.[5]

A second rodent programme targeted the gut. Because the receptor ipamorelin binds is the ghrelin receptor, and ghrelin promotes gastrointestinal motility, investigators tested it in a rat model of postoperative ileus. A single intravenous dose shortened time to first bowel movement, and repeated dosing increased cumulative fecal output, food intake, and body weight gain over 48 hours.[7] Separately, ipamorelin evoked insulin release from pancreatic tissue fragments of normal and diabetic rats through calcium-channel and adrenergic pathways.[6]

Human evidence exists, and it is two studies. The first characterized pharmacokinetics and GH response across five infusion rates in healthy male volunteers.[3] The second is the one that matters most: a phase 2, multicenter, double-blind, placebo-controlled trial of intravenous ipamorelin for postoperative ileus in patients undergoing bowel resection. One hundred seventeen patients were enrolled, 114 analyzed. Median time to first tolerated solid meal was 25.3 hours on ipamorelin and 32.6 hours on placebo, a difference that did not reach significance (p = 0.15). No secondary efficacy endpoint separated the arms either.[8]

That trial is the single most informative document in the ipamorelin literature, and it is a negative result. A promising rodent motility signal, taken into a properly randomized human trial, did not reproduce. Development stopped there.

Where the evidence is weak

Ipamorelin was tested in humans for one thing, and it did not work. This is unusual among research peptides and deserves emphasis rather than burial. Most grey-market compounds have never been tested against a clinical endpoint at all; ipamorelin was, in a multicenter phase 2 trial, and the endpoint was missed.[8] Nothing about that result speaks to recovery, body composition, or sleep, but it does show what happens when this compound's animal data meets a controlled human design.

Nothing ipamorelin is currently marketed for has ever been studied in people. There is no published trial of ipamorelin for muscle mass, fat loss, injury recovery, sleep quality, or aging. A 2026 independent review of peptides sold direct to patients in sports medicine names ipamorelin among the unapproved compounds where favorable animal findings have not been matched by rigorous human data, and warns explicitly about the potential for harm.[12]

The rodent bone work does not transfer cleanly. The longitudinal bone-growth result was obtained in animals whose growth plates were still responsive, and total IGF-1 did not change, which the authors themselves flagged as a puzzle. The glucocorticoid study is a catabolic-rescue model, not a model of a healthy adult seeking an improvement.[2][5]

Longest human exposure on record: seven days. All of it intravenous, all of it inpatient, all of it monitored. There is no published experience with subcutaneous self-administration over any period, which is how the compound is actually used outside research.[8]

Identity is not settled. Analysis of growth-promoting products circulating outside the regulated supply chain identified glycine-extended analogs of GHRP-6, GHRP-2, and ipamorelin, with the modified ipamorelin identity confirmed by custom synthesis.[10] A compound with no approved manufacturer has no release specification, and the published analytical work exists precisely because investigators could not assume what was in a preparation.

Legal and regulatory status

Ipamorelin is not approved by the FDA for any indication, and no regulator has approved it anywhere. It reached phase 2 clinical development for postoperative ileus under a registered trial protocol and did not proceed after that trial missed its primary endpoint.[8] It is not a dietary supplement ingredient and it is not an approved drug; material carrying the name is distributed for laboratory research use, which is why every mention of it on this site carries research-only framing.

In tested sport the position is explicit rather than inferred. The World Anti-Doping Agency names ipamorelin on the prohibited list itself, as an example of a growth hormone secretagogue under section S2.2.4, and every substance in section S2 is prohibited at all times, in competition and out of it, as a non-specified substance. That status is enforceable: published analytical methods identify ipamorelin metabolites in human urine after administration,[9] and doping-control laboratories also monitor modified analogs of the peptide found in growth-promoting preparations.[10] Any athlete competing under an anti-doping code should still check the current year's prohibited list directly rather than rely on this page.

What the regulatory status means for a reader is narrower and more useful than any argument about enforcement: there is no label, no approved manufacturer, no assigned indication, and no regulated quality standard behind anything sold as ipamorelin. PHL does not sell peptides and takes no position on how unapproved material reaches anyone.

Questions to bring to a provider

The useful conversation starts from the problem, not the molecule. Questions worth raising:

  • Is the actual complaint recovery, sleep, body composition, or joint pain, and what does the standard-of-care evidence base offer for it?
  • Given that the only randomized human trial of this compound measured a gastrointestinal endpoint and missed it, what would count as evidence that it helps with anything else?[8]
  • Does a personal or family history of malignancy change the calculus, given the cohort associations between circulating IGF-1 and cancer risk?[11]
  • With diabetes, prediabetes, or glucose-lowering medication in the picture, what should be watched, given the effects of this class on insulin secretion and of growth hormone on insulin action?[6]
  • Which baseline and follow-up tests (IGF-1, fasting glucose, HbA1c) would make it possible to tell whether anything actually changed?
  • If competing in a tested sport, what does the current prohibited list say, and how is this class detected?[9]

A clinician who says "this one was tried properly once and did not work" is citing the literature accurately.

Evidence by claim

Grades describe how strong the evidence is; the line under each grade describes what kind of studies it is. How we grade evidence.

Growth hormone release in humans
Human RCT evidence human RCT

A dose-escalation study in healthy male volunteers characterized both the pharmacokinetics (dose-proportional, terminal half-life about two hours) and the GH response, which occurred at every dose level as a single episode peaking around 40 minutes and declining to negligible concentrations afterwards. This establishes that the compound does what it is designed to do in people; it establishes nothing beyond that.

[3]

Postoperative ileus after bowel resection
Human RCT evidence human RCT

The only clinical-outcome trial ever run on ipamorelin was a phase 2, multicenter, double-blind, placebo-controlled study in 114 analyzed patients. Median time to first tolerated solid meal was 25.3 hours on ipamorelin versus 32.6 hours on placebo, a difference that was not statistically significant (p = 0.15), and no secondary efficacy analysis separated the groups either. This is a negative trial, and it is the highest-quality human evidence the compound has.

[8]

Selective GH release without ACTH or cortisol elevation
Animal studies only animal

In cultured rat pituitary cells, anaesthetized rats, and conscious swine, ipamorelin released GH with potency and efficacy comparable to GHRP-6 while leaving ACTH and cortisol unchanged even at doses more than 200-fold above its GH-releasing ED50, and leaving FSH, LH, prolactin, and TSH unaffected. That is unusual for the class.

[1]

Bone growth and bone mineral content
Animal studies only animal

In adult female rats, ipamorelin dose-dependently increased longitudinal bone growth rate and body weight gain without changing total IGF-1 or markers of bone turnover; over 12 weeks of continuous infusion it increased bone mineral content; and in a three-month glucocorticoid model it counteracted the steroid-induced fall in periosteal bone formation. Consistent rodent findings, with no human counterpart.

[2] [4] [5]

Gastrointestinal motility
Animal studies only animal · human RCT

In a rat model of postoperative ileus, single-dose ipamorelin shortened time to first bowel movement and repeated dosing increased cumulative fecal output, food intake, and weight gain. The human trial built on this preclinical rationale did not reproduce the benefit, which is a useful worked example of how far a positive rodent model carries.

[7] [8]

Recovery, body composition, sleep, or anti-aging benefit in humans
Anecdotal reports only review

No published trial has tested any of these outcomes for ipamorelin. The uses it is marketed for rest on mechanism plus community report, and a 2026 independent review of peptides sold direct to patients places it among the unapproved compounds where animal-model promise has not been matched by human data.

[12]

FOR RESEARCH PURPOSES ONLY

Typical protocol range in the research

  • Human dose-escalation pharmacokinetic and pharmacodynamic study in healthy male volunteers, eight subjects at each of five levels, given as a 15-minute intravenous infusion

    4.21, 14.02, 42.13, 84.27, and 140.45 nmol per kilogram of body weight; GH release occurred at every level, peaking about 40 minutes after the infusion [3]

  • Phase 2 randomized, double-blind, placebo-controlled trial in adults undergoing bowel resection, dosed for up to seven days

    0.03 mg per kilogram of body weight by intravenous infusion twice daily [8]

  • Adult female rats, subcutaneous injection three times daily for 15 days

    18, 90, and 450 µg per day, producing a dose-dependent increase in longitudinal bone growth rate [2]

Every published human dose above was given intravenously in a hospital or clinical-pharmacology setting, and the endpoints were hormone concentrations and time to tolerate a meal, not the outcomes ipamorelin is marketed for. No published trial establishes a subcutaneous protocol for any human indication. The microgram figures that circulate in community discussion have no published trial behind them and are therefore not reported here.

Ranges are what published research reports, not a recommendation. PHL does not prescribe, and nothing here is personalized to you.

Side effects & safety signals

  • No long-term human safety data

    Not established · The longest published human exposure is seven days of inpatient dosing. In that trial treatment-emergent adverse events were common in both arms (87.5% on ipamorelin, 94.8% on placebo) and the authors concluded the compound was well tolerated over that window. Nothing in the published record addresses weeks, months, or years of use, and independent review characterizes human safety data for unapproved peptides in this class as scarce.

    [8] [12]

  • Growth-hormone axis stimulation and the malignancy question

    The GH release itself is the intended and reproducible effect · Ipamorelin raises GH in humans and in every species tested. Large prospective cohort work links higher circulating IGF-1, the main downstream product of GH, to the risk of several cancers. That association is drawn from people taking nothing and is not a measured effect of this compound, but a personal or family history of malignancy is a reason to raise any growth-hormone secretagogue with a clinician before considering anything.

    [3] [11]

  • Insulin release and glucose handling

    Demonstrated ex vivo in rat pancreatic tissue · Ipamorelin evoked significant insulin secretion from pancreatic tissue fragments of both normal and diabetic rats, acting through calcium-channel and adrenergic pathways. Growth hormone itself opposes insulin action. Neither effect has been characterized in humans on this compound, which makes existing diabetes, prediabetes, or glucose-lowering medication a provider-discussion flag rather than a settled interaction.

    [6] [3]

  • Selectivity is a documented advantage, and a narrow one

    Consistently reported in the preclinical work · Unlike GHRP-6 and GHRP-2, ipamorelin did not raise ACTH or cortisol in swine even at doses more than 200-fold above the GH-releasing ED50, and it did not move FSH, LH, prolactin, or TSH. That is a real finding and the reason the compound was considered a clinical candidate. But it is a finding about what ipamorelin does not do in pigs, not a demonstration of safety in people.

    [1]

  • Unverified identity of material carrying this name

    Not quantified · Analysis of growth-promoting products seized outside the regulated supply chain identified N-terminally glycine-extended analogs of GHRP-6, GHRP-2, and ipamorelin, with the glycyl-ipamorelin identity confirmed by custom synthesis. With no approved manufacturer there is no release specification, so nothing guarantees that a vial holds the molecule its label names.

    [10]

  • Prohibited in tested sport, and detectable

    Standing status · Ipamorelin is named on the World Anti-Doping Agency prohibited list itself, as an example of a growth hormone secretagogue under section S2.2.4, and everything in section S2 is prohibited at all times, in competition and out of it. Published methods identify ipamorelin metabolites in human urine after administration, so the status is enforceable rather than nominal. Any athlete in a tested sport should confirm the current year's prohibited list rather than rely on this page.

    [9] [10]

Published lists are never exhaustive, so report anything unexpected to a licensed provider.

Storage, handling & reconstitution

Lyophilized storage
Lyophilized ipamorelin is conventionally kept refrigerated at 2–8 °C and protected from light, with freezing used for long-term holding. The published pharmacokinetic work describes a terminal half-life of about two hours in circulation; it says nothing about shelf life in a vial. The handling conventions here come from general lyophilized-peptide practice, not from an ipamorelin stability study.
Reconstituted storage
Once in solution, peptides are conventionally refrigerated at 2–8 °C, protected from light, and treated as short-dated rather than indefinitely stable. No published study establishes a solution shelf life for ipamorelin.
Reconstitution diluent
The conventional diluent for lyophilized research peptides, including ipamorelin, is bacteriostatic water: sterile water preserved with 0.9% benzyl alcohol. Sterile water without a preservative is used where a preservative is contraindicated and is treated as single-use.
Reconstitution & handling
Conventional handling: sanitize the stopper before piercing it, add the diluent slowly down the inside wall of the vial rather than directly onto the powder, and let it dissolve on its own. Swirl gently if needed; never shake. A properly reconstituted solution is clear; anything cloudy, discolored, or carrying visible particulate is discarded. PHL does not publish volume or unit calculations, because those are dosing decisions and dosing decisions belong with a licensed clinician.
Handling notes
Ipamorelin was developed to an investigational standard and then dropped; there is no marketed product, no label, no assigned beyond-use date, and no lot-level stability data behind material sold under the name today. Doping laboratories examining growth-promoting preparations have identified modified analogs circulating alongside the parent peptide; one is an N-terminally extended glycyl-ipamorelin. Identity itself is not a settled question. Treat all of the above as convention, not specification.

The how-to guides cover the conventions behind these fields, and what the published stability data does and does not establish: Storage, Reconstitution, Handling.

Goal pages that include Ipamorelin

Each one starts from the goal rather than the molecule, and grades what the evidence supports for that goal specifically.

  • Endurance

    A research reference for the compounds mapped to aerobic capacity and stamina. Every one of them is prohibited in tested sport at all times, and only one has a randomized human trial using an endurance endpoint.

  • Gut Healing

    A research reference for the peptides mapped to gut healing and intestinal repair. It covers what the rodent colitis literature established, why almost none of it has been tested in people, and what "healing the gut lining" does and does not mean in the published record.

  • Recovery

    A research reference for the peptides mapped to injury recovery and tissue repair, covering what the animal literature established, what the handful of human trials actually measured, and how to tell the two apart.

Questions for your provider

Bring this page to a licensed provider. A provider can order labs, review your medications and history, and tell you whether anything here is relevant to your situation. This page can't. Peptide Health Lab does not prescribe and does not sell peptides.

Want a structured starting point for that conversation? The Stack Builder turns your goals into a research-cited outline you can review together.

Citations

12 sources · every identifier checked against PubMed

Before you act on any of this

This page is educational only and is not medical advice. It does not diagnose, treat, or prescribe. Review it with a licensed provider before making any health decision. Peptide Health Lab does not sell peptides.

How we grade and verify evidence · Terms of Use · Privacy Policy

Open the Stack Builder