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Ipamorelin — research-grade lyophilized peptide vial from Peptide.Express, ≥99% HPLC purity
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Ipamorelin — Selective GHSR-1a Agonist | 5-Amino Acid Growth Hormone Secretagogue Pentapeptide

Research-Grade Compound

Ipamorelin is a synthetic pentapeptide and selective agonist at the growth hormone secretagogue receptor GHSR-1a, the receptor endogenous ghrelin acts on. Sequence Aib-His-D-2-Nal-D-Phe-Lys-NH2, molecular formula C38H49N9O5, molecular weight 711.85 Da, CAS 170851-70-4. It belongs to the growth hormone releasing peptide (GHRP) class.

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≥99% by HPLCLC-MS/MS VerifiedCoA Every BatchIn-Vitro Research Use Only

What is Ipamorelin?

Ipamorelin is a synthetic pentapeptide and selective agonist at the growth hormone secretagogue receptor GHSR-1a, the receptor endogenous ghrelin acts on. Sequence Aib-His-D-2-Nal-D-Phe-Lys-NH2, molecular formula C38H49N9O5, molecular weight 711.85 Da, CAS 170851-70-4. It belongs to the growth hormone releasing peptide (GHRP) class.

Three of its five residues are non-natural. Aib (alpha-aminoisobutyric acid), D-2-naphthylalanine and D-phenylalanine are all chosen for the same two reasons: they resist proteolysis, and they lock the peptide backbone into a conformation that favours GHSR-1a over the other targets earlier GHRPs also hit. A five-residue peptide is a small molecule by peptide standards — at 711.85 Da ipamorelin is closer in mass to a conventional small-molecule drug than to the 3–5 kDa GHRH analogs it is usually studied beside.

The property ipamorelin is known for is selectivity. Raun and colleagues characterised it as the first selective growth hormone secretagogue, meaning it drives GH release without the cortisol, ACTH and prolactin elevation that GHRP-2 and GHRP-6 produce. That claim comes from a defined dose range in the original preclinical work, and it is worth reading it that way rather than as an absolute property — selectivity in receptor pharmacology is nearly always concentration-dependent, and the modern human data needed to define where ipamorelin's selectivity window ends has not been published.

How Does Ipamorelin Work? Mechanism of Action

Ipamorelin binds GHSR-1a on anterior pituitary somatotrophs. Unlike GHRH-R, which couples to Gs and works through cAMP, GHSR-1a couples to Gq. Receptor occupancy activates phospholipase C, which cleaves PIP2 into IP3 and diacylglycerol. IP3 releases calcium from intracellular stores, DAG activates protein kinase C, and the resulting rise in cytosolic calcium triggers exocytosis of growth hormone granules. The end result looks like what a GHRH analog produces; the route there is a different second-messenger system entirely.

That mechanistic separation is why GHRH analogs and GHRPs are studied together. Two receptors, two G-proteins, two second messengers, one shared output. Co-stimulation of GHRH-R and GHSR-1a produces a GH response larger than either pathway generates alone — a finding replicated across the broader GHRH-plus-GHRP literature, though not specifically for every commercial pairing sold as a stack.

Ipamorelin also suppresses somatostatin tone at the pituitary, which is the second half of the ghrelin-receptor story and is frequently left out of vendor descriptions. Somatostatin is the brake on somatotroph firing; reducing it removes an inhibition rather than adding a stimulus. Two mechanisms acting on the same cell in the same direction.

On selectivity: the earlier GHRPs activate GHSR-1a but also produce measurable ACTH, cortisol and prolactin release, which confounds any experiment where the hypothalamic-pituitary-adrenal axis is a variable. Ipamorelin was engineered to drop those off-target effects, and in the preclinical characterisation it largely does. The honest framing for a research protocol is that ipamorelin has a wider clean window than GHRP-2 or GHRP-6, not that it has no ceiling — a compound with no measured cortisol effect at the doses tested is not the same as a compound with no cortisol effect.

Reported plasma half-life is approximately 2 hours, which is long for a peptide this small and reflects the protease resistance built into the non-natural residues. The half-life figures circulating for ipamorelin come from a limited set of studies, so treat the number as an approximate planning value rather than a precise pharmacokinetic constant.

Research Applications of Ipamorelin

Ghrelin Receptor Pharmacology

  • GHSR-1a agonism assays: calcium mobilization in transfected cell lines is the direct receptor readout, measured independently of any GH endpoint.
  • Selectivity profiling: running ipamorelin against GHRP-2 and GHRP-6 with ACTH, cortisol and prolactin panels is how the selectivity claim is tested rather than assumed.
  • Somatostatin tone studies: ipamorelin reduces somatostatin-mediated inhibition at the pituitary, which is a separate readout from direct somatotroph stimulation.

Growth Hormone Secretagogue Research

  • Dual-pathway co-stimulation: pairing ipamorelin with a GHRH analog activates Gq and Gs signaling on the same somatotroph, and the combined response is larger than either alone.
  • Cortisol-sensitive experimental designs: where HPA axis activation would confound the endpoint, ipamorelin is the GHRP chosen specifically because it minimises that confound.
  • IGF-1 downstream measurement: hepatic IGF-1 output following GHSR-1a-driven GH release is the standard secondary endpoint.

Comparative Secretagogue Design

  • GHSR-1a versus GHRH-R: ipamorelin and sermorelin have identical downstream output and completely different receptors, which makes the pair a clean tool for attributing an effect to a signaling route.
  • Peptide size and stability: at 711.85 Da with three non-natural residues, ipamorelin behaves very differently in solution and in plasma from a 3 kDa GHRH analog.
  • Ghrelin comparison: ipamorelin engages GHSR-1a without ghrelin's acyl modification, separating receptor agonism from the wider metabolic signaling ghrelin carries.

Ipamorelin vs Sermorelin

FeatureIpamorelinSermorelin
Compound classGHRP / growth hormone secretagogueGHRH analog
Receptor targetGHSR-1a (ghrelin receptor)GHRH-R
G-protein couplingGqGs
Second messengerPLC → IP3 / DAG → calcium, PKCAdenylyl cyclase → cAMP → PKA
Amino acid count5 (pentapeptide)29
SequenceAib-His-D-2-Nal-D-Phe-Lys-NH2GRF(1-29) NH2
Molecular formulaC38H49N9O5C149H246N44O42S
Molecular weight711.85 Da3,357.9 Da
CAS number170851-70-486168-78-7
Approximate plasma half-life~2 hours10–20 minutes
Cortisol / prolactin effectMinimal in preclinical characterisationNot a feature of GHRH-R agonism
Somatostatin interactionReduces somatostatin toneCounter-regulated by somatostatin
FDA statusNot approved for any indicationPrior approval as Geref, withdrawn 2008
WADA statusProhibited at all timesProhibited at all times

The output is the same and almost nothing else is. Ipamorelin works through Gq and calcium; sermorelin works through Gs and cAMP. Substituting one for the other in a protocol does not produce a comparable experiment — it produces a different one. Running both is how the contribution of each pathway gets separated.

Read the full ipamorelin vs sermorelin comparison

Ipamorelin Technical Specifications

Technical specifications for Ipamorelin, including molecular data, purity standard, testing methods and storage requirements.
Compound NameIpamorelin
Common SynonymsIpamorelin acetate, ipamorelin peptide
ClassificationGHRP (growth hormone releasing peptide) / GH secretagogue
Receptor TargetGHSR-1a (growth hormone secretagogue receptor 1a, the ghrelin receptor)
CAS Number170851-70-4
Molecular FormulaC38H49N9O5
Molecular Weight711.85 Da
Amino Acid SequenceAib-His-D-2-Nal-D-Phe-Lys-NH2
Amino Acid Count5 (pentapeptide)
Non-Natural ResiduesAib (alpha-aminoisobutyric acid), D-2-naphthylalanine, D-phenylalanine
Approximate Plasma Half-Life~2 hours (reported)
Selectivity NoteMinimal cortisol, ACTH or prolactin release in preclinical characterisation
Purity≥99% by HPLC
Purity ConfirmationLC-MS/MS molecular weight verification
Endotoxin TestingLAL (Limulus Amebocyte Lysate) method
Physical FormLyophilized powder
AppearanceWhite to off-white powder
ReconstitutionBacteriostatic water or sterile 0.9% sodium chloride
Storage (lyophilized)-20°C, desiccated, protected from light
Storage (reconstituted)2–8°C, use within 14–28 days
Shelf Life24 months from manufacture (lyophilized)
Testing MethodsHPLC, LC-MS/MS, LAL Endotoxin
DocumentationCertificate of Analysis (CoA) per batch
FDA StatusNot approved for any human indication
WADA StatusProhibited at all times (growth hormone secretagogues)
Intended UseIn-vitro laboratory research only

How to Reconstitute Ipamorelin for Research

Ipamorelin is the easiest peptide in this group to reconstitute — at 711.85 Da it dissolves almost immediately, often before the swirl is finished. The offsetting problem is that small vial masses of a low-molecular-weight peptide produce a barely visible lyophilized cake, so it is easy to assume a vial is empty or under-filled when it is neither. Check the vial against the light before adding diluent, and weigh the batch record rather than the appearance.

  1. Bring the vial to room temperature before opening.
  2. Draw the calculated volume of bacteriostatic water. For a 5 mg vial, 2 mL yields 2.5 mg/mL and 2.5 mL yields 2 mg/mL. For a 10 mg vial, 2 mL yields 5 mg/mL.
  3. Swab the septum with alcohol and allow 30 seconds to dry.
  4. Inject the diluent slowly against the inner vial wall.
  5. Swirl gently for 30–60 seconds. Ipamorelin dissolves quickly and does not need extended agitation. Do not shake.
  6. Confirm the solution is clear and colorless. Discard if cloudy, discolored, or if particulate is visible.
  7. Label with the reconstitution date and resulting concentration.
  8. Store at 2–8°C and use within 14–28 days. Avoid repeated freeze-thaw cycles.

Diluent: bacteriostatic water for peptide reconstitution. Full protocol: step-by-step peptide reconstitution guide. Concentration maths: peptide reconstitution calculator.

Frequently Asked Questions — Ipamorelin

What is ipamorelin?

Ipamorelin is a synthetic pentapeptide (Aib-His-D-2-Nal-D-Phe-Lys-NH2, 711.85 Da, CAS 170851-70-4) that acts as a selective agonist at GHSR-1a, the ghrelin receptor. It belongs to the growth hormone releasing peptide class and is studied as a GH secretagogue in laboratory research.

What is ipamorelin's mechanism of action?

It binds GHSR-1a on pituitary somatotrophs. The receptor couples to Gq, activating phospholipase C, which generates IP3 and diacylglycerol. IP3 releases calcium from intracellular stores and DAG activates protein kinase C; the calcium rise triggers GH granule exocytosis. Ipamorelin also reduces somatostatin tone at the pituitary, removing an inhibitory brake in parallel with the direct stimulus. Note that this is an entirely different second-messenger route from the cAMP-PKA cascade a GHRH analog uses.

How is ipamorelin different from GHRP-2 or GHRP-6?

All three are GHSR-1a agonists. GHRP-2 and GHRP-6 also produce measurable ACTH, cortisol and prolactin release, which contaminates any experiment where the HPA axis is a variable. Ipamorelin was designed to drop those off-target effects, and in the preclinical characterisation it does so across the dose range tested.

Does ipamorelin affect cortisol?

In the original preclinical characterisation, not meaningfully — that finding is what earned it the "selective" designation. The caveat researchers should carry is that selectivity in receptor pharmacology is concentration-dependent, and the studies establishing this used a defined dose range. A protocol operating outside that range should measure cortisol rather than assume it stays flat.

What is ipamorelin's half-life?

Approximately 2 hours in plasma — long for a 711.85 Da peptide, and a direct consequence of the three protease-resistant non-natural residues in the sequence. The published pharmacokinetic dataset behind that figure is limited, so treat it as a planning estimate rather than a fixed constant.

What is the difference between ipamorelin and sermorelin?

Different receptors and different signaling. Ipamorelin is a 5-residue GHSR-1a agonist (711.85 Da) working through Gq, phospholipase C and calcium. Sermorelin is a 29-residue GHRH-R agonist (3,357.9 Da) working through Gs, adenylyl cyclase and cAMP. Both end in GH release from the same cell, which is why they are studied together rather than as substitutes.

Can ipamorelin and CJC-1295 be studied together?

That combination is the most common GH secretagogue research pairing, and the rationale is sound: CJC-1295 No DAC hits GHRH-R through cAMP while ipamorelin hits GHSR-1a through calcium, so the two signals are independent until they converge on the somatotroph. The broader GHRH-plus-GHRP literature supports a larger combined GH response than either produces alone. Combination pharmacokinetic data for the specific pre-blended product does not exist, and any protocol using it is inferring from single-compound work.

Is ipamorelin the same as GHRP-5?

Some vendor listings apply the GHRP-5 label to ipamorelin. That designation does not appear in the primary ipamorelin literature, which describes the compound simply as a selective growth hormone secretagogue. Treat the alias as a marketplace convention rather than a chemical identity, and verify what you have by molecular weight — 711.85 Da — rather than by name.

Does ipamorelin increase IGF-1?

Indirectly. GHSR-1a agonism raises GH, and GH drives hepatic IGF-1 transcription through JAK2-STAT5 signaling. IGF-1 is a downstream secondary endpoint in ipamorelin research rather than a direct pharmacological action of the peptide.

Is ipamorelin WADA prohibited?

Yes, at all times, in and out of competition. Growth hormone secretagogues acting at the ghrelin receptor fall under the World Anti-Doping Agency's growth hormone releasing factors category, and ipamorelin is named there.

What purity standard does Peptide.Express use for ipamorelin?

≥99% by reverse-phase HPLC with LC-MS/MS confirming the 711.85 Da molecular weight. Small peptides with non-natural residues carry a specific synthesis risk — incomplete D-amino acid incorporation produces diastereomers that share a mass with the target compound, so chromatographic resolution matters as much as the mass number on the CoA.

What testing does ipamorelin undergo before shipping?

Reverse-phase HPLC for purity, LC-MS/MS for molecular weight identity, LAL endotoxin testing, and visual QC. All performed by an independent third-party laboratory with a batch-specific Certificate of Analysis issued per lot.

How should ipamorelin be stored before and after reconstitution?

Lyophilized: -20°C, desiccated, protected from light, stable for 24 months. Reconstituted: 2–8°C, used within 14–28 days. Do not freeze the reconstituted solution and avoid repeated freeze-thaw cycles.

Where is the Certificate of Analysis for ipamorelin?

On this page and in the Peptide.Express lab results library. Each CoA is batch-specific and lists HPLC purity, LC-MS/MS mass confirmation, endotoxin result, testing laboratory and test date.

Research References

  1. Raun K, et al. "Ipamorelin, the First Selective Growth Hormone Secretagogue." European Journal of Endocrinology, 1998. Read the Raun ipamorelin selectivity study on PubMed
  2. Smith RG, et al. "Modulation of Pulsatile GH Release Through a Novel Receptor in Hypothalamus and Pituitary Gland." Recent Progress in Hormone Research, 1996. Read the GH secretagogue receptor and phospholipase C signaling review on PubMed
  3. Bowers CY, Momany FA, Reynolds GA, Hong A. "On the In Vitro and In Vivo Activity of a New Synthetic Hexapeptide That Acts on the Pituitary to Specifically Release Growth Hormone." Endocrinology, 1984. Read the founding Bowers GHRP hexapeptide study on PubMed

All products are sold for in-vitro laboratory research use only. Not intended for human consumption, clinical use, or veterinary use. Peptide.Express makes no medical claims. Consult the published literature for research application guidance.

Further Reading

Related Research Compounds

CJC-1295 + Ipamorelin (No DAC)The pre-blended dual-pathway stack pairing ipamorelin with a stabilised GHRH analog.SermorelinThe GHRH-R counterpart — same GH output, entirely different receptor and second messenger.TesamorelinFDA-approved GHRH analog studied alongside ipamorelin in dual-pathway designs.Bacteriostatic WaterBenzyl-alcohol-preserved sterile water for reconstituting lyophilized peptide vials.