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Ipamorelin

A selective ghrelin-receptor (GHS-R1a) agonist peptide, studied as a growth-hormone secretagogue. Not FDA-approved for any indication.

Research Article Compound Hubs 2 min read

Mechanism

A different door into the same axis

Ipamorelin acts on a different receptor from a GHRH analogue, and researchers have studied both as separate routes into growth-hormone release.

Step 1 Pentapeptide

Ipamorelin

Five amino acids. The sequence is the one stated in the 1998 characterisation cited below; the drawing itself is a schematic.Schematic diagram: a five-bead peptide backbone labelled Ipamorelin, with the published residue sequence Aib, His, D-2-Nal, D-Phe, Lys-NH2 marked under the beads. The drawing is a schematic and does not depict a molecular structure.CompoundIpamorelinA five-residue peptideAibHisD-2-NalD-PheLys-NH₂
Five amino acids. The sequence is the one stated in the 1998 characterisation cited below; the drawing itself is a schematic. Hold any part of the figure to follow its route Press and hold any part of the figure to follow its route Schematic backbone. Residue labels are the published sequence from the cited characterisation; the drawing is not a structure.

What you're seeing

A short laboratory-made peptide, five amino acids long, studied as a growth-hormone secretagogue: a substance that prompts the release of growth hormone.

Scientific detail

Sequence Aib-His-D-2-Nal-D-Phe-Lys-NH2. It was described in 1998 as the first selective growth hormone secretagogue, releasing growth hormone from primary rat pituitary cells with potency and efficacy comparable to the earlier peptide GHRP-6.

Terminology What is a peptide, and how is it different from a protein?

Source Raun K. et al. — Ipamorelin, the first selective growth hormone secretagogue (European Journal of Endocrinology, 1998)

Step 2 The pituitary gland

Where this happens

The pituitary is a small gland at the base of the brain, and it is where growth hormone is made and stored.Orientation diagram: a simplified cranial outline with the brain inside it and the brainstem descending. The pituitary gland is marked as a small node at the base of the brain and labelled as where growth hormone is made.Where this happensPituitary glandWhere GH is made
The pituitary is a small gland at the base of the brain, and it is where growth hormone is made and stored. A simplified orientation figure, not an anatomical illustration and not to scale. It marks the gland the cited work studied; it does not depict a person.

What you're seeing

The pituitary is a small gland at the base of the brain, and it is where growth hormone is made and stored. The receptor this compound acts on is found there.

Scientific detail

The 1998 characterisation cited below reported growth-hormone release from primary rat pituitary cells. The figure is a simplified orientation drawing marking that gland — not an anatomical illustration, and not to scale.

Terminology What are receptors, ligands, agonists, and antagonists?

Source Raun K. et al. — Ipamorelin, the first selective growth hormone secretagogue (European Journal of Endocrinology, 1998)

Step 3 Ghrelin receptor

GHS-R1a

A different receptor from the one a GHRH analogue uses. That difference is the whole point of the compound.Comparison diagram: two receptors set in cell membranes side by side. The left one, the GHRH receptor — the route a GHRH analogue uses — is drawn dimmed. The right one, GHS-R1a, the ghrelin receptor and ipamorelin's route, is drawn active. Both routes bend inward to the same outcome: the same growth hormone.Two routes, one axisGHRH receptora GHRH analogue's routeGHS-R1aipamorelin's routeThe same growth hormone
A different receptor from the one a GHRH analogue uses. That difference is the whole point of the compound.

What you're seeing

The receptor that ghrelin — the hormone best known for hunger signaling — normally acts on. This is the step that makes ipamorelin mechanistically different from a GHRH analogue.

Scientific detail

Growth hormone secretagogue receptor, subtype 1a. A GHRH analogue such as tesamorelin acts on the separate GHRH receptor. Two different receptors, one shared downstream hormone: studying a selective agonist at this receptor is how researchers isolate this specific route from the other.

Terminology What are receptors, ligands, agonists, and antagonists?

Source Raun K. et al. — Ipamorelin, the first selective growth hormone secretagogue (European Journal of Endocrinology, 1998)

Step 4 Downstream of the receptor

Pituitary signaling

Selectivity is the research interest: a signal that can be attributed to this pathway rather than to several at once.Schematic diagram: inside a pituitary cell, an activated GHS-R1a receptor at the upper membrane sends a signal downward, and growth hormone is released from the lower membrane in separate bursts.Pituitary cellGHS-R1a activatedSignaling in the pituitaryGrowth hormone released
Selectivity is the research interest: a signal that can be attributed to this pathway rather than to several at once.

What you're seeing

Activating the receptor sets off signaling in the pituitary gland, which is where growth hormone is made and stored.

Scientific detail

The selectivity reported in the original characterisation is the point of research interest: a secretagogue that acts on this receptor without broadly disturbing other pituitary hormones lets a study attribute what it observes to this pathway rather than to several at once.

Terminology What are receptors, ligands, agonists, and antagonists?

Source Raun K. et al. — Ipamorelin, the first selective growth hormone secretagogue (European Journal of Endocrinology, 1998)

Step 5 What is measured

Growth-hormone release

The measurable end of the pathway, and how much is actually known about it. Human research is limited and it is not approved for any use.Schematic diagram: growth-hormone release is the measurable end of the pathway, and the figure sets out where it has been measured — in cells, in animals, in limited human data — and that the compound is not approved.PathwayGrowth-hormone releasewhat studies measureMeasured in cellsMeasured in animalsLimited human dataNot approved
The measurable end of the pathway, and how much is actually known about it. Human research is limited and it is not approved for any use. Tissues named in the cited labeling. The figure shows where the signal acts, not what it produces in a person.

What you're seeing

The measurable end of the pathway. Human research on ipamorelin is limited, and it is not approved for any use.

Scientific detail

Pharmacokinetic and pharmacodynamic work in human volunteers has been published, along with preclinical work in a rodent model of post-operative ileus. A phase 2 trial in patients after abdominal surgery did not meet its endpoint, and development for that indication did not continue. Ipamorelin has never received FDA approval for any indication.

Terminology What do pharmacology, pharmacokinetics, and pharmacodynamics mean? How does research move from a lab bench to a clinical trial, and why do results sometimes not translate?

Source Pharmacokinetic-pharmacodynamic modeling of ipamorelin in human volunteers (1999) Efficacy of ipamorelin in a rodent model of postoperative ileus (2009) FDA — Certain bulk drug substances for use in compounding that may present significant safety risks

That is the mechanism in brief. The rest of this page is the detail.

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Go deeper into the science.

Discover the compounds, pathways and research systems connected to what you're already exploring.

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    The GHRH-analogue route into the same growth-hormone axis — the comparison this page draws, seen from the other side.

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Research systems Endocrine signaling

These are separate research materials with separate research records. Nothing here suggests combining them, and no connection above is a claim about using more than one.

Simplified pathway, drawn for educational purposes. It shows what published research describes about the molecule. It does not describe a result in a person, and it is not a claim about NuePharma material.

What research has established

  1. Preclinical research Published

    The original 1998 characterisation reported growth-hormone release from primary rat pituitary cells and in animal models, with selectivity for growth hormone that distinguished it from earlier secretagogues. Later preclinical work examined it in a rodent model of post-operative ileus.

    Source Raun K. et al. — Ipamorelin, the first selective growth hormone secretagogue (European Journal of Endocrinology, 1998) Efficacy of ipamorelin in a rodent model of postoperative ileus (2009)

  2. Human research Limited

    Limited. Pharmacokinetic and pharmacodynamic work in human volunteers has been published. A phase 2 trial in patients after abdominal surgery did not meet its endpoint, and development for that indication did not continue. There is no large-scale clinical program of the kind that supports an approved medicine.

    Source Pharmacokinetic-pharmacodynamic modeling of ipamorelin in human volunteers (1999)

  3. Regulatory status Not approved

    Never approved by the FDA for any indication. Its status as a substance eligible for pharmacy compounding has been reviewed more than once; rather than fix a snapshot here, the current position is published by the FDA directly.

    Source FDA — Certain bulk drug substances for use in compounding that may present significant safety risks

Sources for this diagram

  1. Raun K. et al. — Ipamorelin, the first selective growth hormone secretagogue (European Journal of Endocrinology, 1998)
  2. Pharmacokinetic-pharmacodynamic modeling of ipamorelin in human volunteers (1999)
  3. Efficacy of ipamorelin in a rodent model of postoperative ileus (2009)
  4. FDA — Certain bulk drug substances for use in compounding that may present significant safety risks

Overview. Ipamorelin is a synthetic peptide studied as a growth hormone secretagogue — a substance that stimulates the release of growth hormone through a mechanism distinct from GHRH analogues such as tesamorelin.

Molecule / class. Ipamorelin is a pentapeptide, and was described in the scientific literature as the first growth hormone secretagogue with selectivity for GH release comparable to that of GHRH, while acting through a different receptor.

Mechanism under investigation. Ipamorelin binds and activates the growth hormone secretagogue receptor, subtype 1a (GHS-R1a) — the same receptor activated by ghrelin, the endogenous hormone best known for its role in hunger signaling and GH release. This is a mechanistically distinct pathway from a GHRH analogue like tesamorelin, which acts on the separate GHRH receptor; researchers have studied both as different entry points into the same broader GH/IGF-1 axis.

Why the pathway is researched. The ghrelin/GH pathway is of research interest for its role in growth hormone regulation and, separately, appetite and energy balance; studying a selective agonist at this receptor lets researchers isolate that specific mechanism from others acting on the same downstream hormone.

Research status. Preclinical data on ipamorelin exists in the published literature. Human research specific to ipamorelin is limited; one Phase 2 randomized controlled trial studying it for a specific post-surgical condition did not meet its endpoint.

Regulatory status. Ipamorelin has never received FDA approval for any indication and is not an approved drug in the United States. Its status specifically as a substance eligible for pharmacy compounding under Section 503A of the Federal Food, Drug, and Cosmetic Act has changed more than once as FDA has reviewed nominations to its bulk drug substances lists — rather than state a specific snapshot here that may already be out of date, the current, authoritative status is published directly by the FDA (linked below).

What remains unknown. Ipamorelin’s effects, safety profile, and appropriate use are not established through the kind of large-scale human clinical trial program that supports an approved medicine.

NuePharma product information. NuePharma’s Ipamorelin listing is 10 mg per vial, supplied lyophilized, for research use only.

Sources & further reading

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