Ipamorelin

What ipamorelin is and how it works

Ipamorelin is a pentapeptide, Aib-His-D-2Nal-D-Phe-Lys-NH₂, catalogued during development as NNC 26-0161. Three of its five residues do not occur in proteins: alpha-aminoisobutyric acid, D-2-naphthylalanine and D-phenylalanine. Together with the amide cap at the C-terminus, they make the molecule awkward for peptidases to recognise, which is how something this small survives in plasma long enough to act. It is not a fragment of any human hormone. It was designed.

The receptor it activates is GHS-R1a, the ghrelin receptor, found on somatotroph cells in the pituitary and on neurons in the hypothalamus. Binding recruits a phospholipase C pathway that raises intracellular calcium and pushes stored growth hormone out of the cell, while hypothalamic signalling reduces somatostatin tone, the brake that normally holds secretion down. This is a separate route from the one GHRH analogues use, which is why the two families are so often studied together. The history is upside down: the growth hormone releasing peptides were built in the 1980s, the receptor was identified in 1996 and its natural ligand, ghrelin, was described in 1999.

Ghrelin-receptor agonists rarely stop at growth hormone. The same receptor sits on cells that govern appetite, and the older peptides in this family also nudge ACTH, cortisol and prolactin upward. Ipamorelin was picked out of a screening programme for the opposite behaviour: a full growth hormone response with the other pituitary hormones left alone.

What the research on ipamorelin shows

The selectivity finding comes from Raun et al. (1998, European Journal of Endocrinology), working in swine. Ipamorelin released growth hormone in a dose-related way, with efficacy in the same range as the older GHRP-6, and produced no meaningful rise in ACTH or cortisol even at doses more than 200-fold above the dose that gave half the maximum growth hormone response. That is a clean result, and it is an animal result. No published human study has mapped the same dose-response curve for cortisol in people.

Human data exist but are narrow. A pharmacology study put the terminal half-life at about two hours after intravenous infusion, short enough to stay closer to a pulse than to the flat elevation a long-acting GHRH analogue produces. The compound was then developed for a surgical indication rather than an endocrine one. Ghrelin-receptor agonists speed gastric emptying and gut motility, so ipamorelin was taken into phase 2 trials for postoperative ileus, the stall in bowel function that follows abdominal surgery.

Where the evidence stops

That programme ended at phase 2 without approval, and no phase 3 followed. What does not exist in the published literature is any controlled human trial of ipamorelin for body composition, tendon or muscle repair, bone density or physical performance. The growth hormone rise is well documented; what it produces downstream, in people, over weeks, is not. Anyone reading a supplier page that promises lean mass is reading marketing, not evidence.

Doses of ipamorelin used in published research

There is no validated human dose for ipamorelin. The animal work is expressed per kilogram and relative to an internal reference dose, which is useful for comparing peptides and useless for anything else; the hospital trials used schedules set for a surgical indication that never completed. These are study designs, not instructions, and the compound is sold for laboratory research only.

Safety and side effects of ipamorelin

No long-term human safety data exist. The points below stay close to what has been measured.

• The selectivity is a pig finding. The absence of an ACTH and cortisol response was established in swine. It is the best evidence available and it is not human evidence.
• Glucose and insulin. Growth hormone opposes insulin, and ghrelin-receptor agonists acutely reduce insulin secretion in human studies. Both effects point the same way, towards higher blood glucose, in a compound nobody has given to people for months.
• Appetite. This is the receptor that drives hunger, and the first-generation peptide in the family is strongly orexigenic. Appetite is not a prominent finding in the ipamorelin literature, but it has not been ruled out either.
• Fluid retention and joint symptoms. Swelling, joint pain and carpal tunnel symptoms follow sustained growth hormone excess. They are class concerns for anything that raises GH output, not observations from ipamorelin trials.
• Sterility and handling. Research vials are lyophilised powder, not licensed injections. Nothing on this page describes a preparation intended for human or veterinary use.

Regulatory status of ipamorelin in Europe

Ipamorelin has no marketing authorisation in the European Union and none anywhere else. Development reached phase 2 and stopped; no regulator has assessed a dossier for it. In the EU a medicine needs an authorisation, granted centrally by the EMA or nationally; material sold as a research peptide has none and is not sold for human use. Rules on possession and on personal imports differ between member states.

For athletes the position is unambiguous. Growth hormone secretagogues, ipamorelin among them, are named in section S2 of the WADA Prohibited List, which applies at all times, in and out of competition. Our guide to growth hormone secretagogues sets ipamorelin beside GHRP-2 and the rest of the family.

Sourcing and quality: ipamorelin for research

King Peptides sells ipamorelin in one form only: the CJC-1295 + Ipamorelin Blend 5/5 mg, which combines it with the GHRH analogue CJC-1295. There is no single-peptide ipamorelin vial in the catalogue. For a blend, read the certificate of analysis with both components in mind. Ipamorelin is small by peptide standards: its mass peak should sit close to the 711.9 Da in the panel, well clear of the much heavier GHRH analogue. Purity should be stated as at least 99% by HPLC, and the lot number on the certificate has to be the lot number on the vial.

Orders are dispatched from the Netherlands, inside the EU, with a lot-specific certificate carrying HPLC and mass spectrometry results. Delivery usually takes 1–2 business days within the Netherlands and 3–5 business days elsewhere in the EU on the shop's own estimate, and there are no customs formalities inside the union; shipments to non-EU destinations such as the UK, Switzerland or Norway can attract import rules and duties. Packaging is neutral and tracked, and buyers confirm at checkout that the order is for research and that they are 18 or older. Our guides to reading a certificate of analysis and to storage and reconstitution cover what to do with the vial once it arrives.

Ipamorelin frequently asked questions

Is ipamorelin a GHRP? In mechanism, yes. It acts on the same receptor as GHRP-6 and GHRP-2 and is usually grouped with them as a later, more selective member of the family. Its sequence is unrelated to theirs.

Does ipamorelin raise cortisol? Not in the swine study that made its reputation, even far above the growth hormone dose. Human dose-response data for cortisol are thin, so the honest answer is that selectivity is well supported in one species and assumed in ours.

Why is it sold together with CJC-1295? The two hit different receptors on the same cell and the combination releases more growth hormone than either alone, which is why almost all of the pairing research uses one of each family.

Was ipamorelin ever a medicine? No. It was tested in people for postoperative ileus, reached phase 2 and went no further. There is no licensed product, no approved indication and no official dosing document anywhere in the world.