Ipamorelin vs sermorelin: secretagogue or GHRH analogue?
Sermorelin is the reference GHRH analogue — the first 29 residues of growth-hormone-releasing hormone, the shortest fragment that keeps full receptor activity. Ipamorelin is a five-residue selective agonist at the ghrelin receptor. They engage different receptors, so the choice follows which half of the axis the question is about.
| Ipamorelin | Sermorelin | |
|---|---|---|
| Receptor | Ghrelin receptor (GHS-R1a) | GHRH receptor |
| Length | 5 residues | 29 residues |
| Molecular weight | 711.9 g/mol | 3357.9 g/mol |
| Parent molecule | Synthetic pentapeptide | GHRH (1-44) fragment |
| Selectivity | No cortisol or prolactin release | GHRH-specific |
| Role in the literature | Selective secretagogue | Reference GHRH analogue |
Why is sermorelin the reference?
At 29 residues it is the minimum fragment of the 44-residue hormone that retains full receptor activity, which makes it the practical synthetic standard. The CJC-1295 variants are this backbone with stabilising substitutions.
What does ipamorelin contribute that sermorelin cannot?
Activity at a different receptor. Any effect present with ipamorelin and absent with sermorelin points at ghrelin receptor signalling rather than GHRH signalling.
How do their sizes affect handling?
A five-residue peptide and a 29-residue one differ in solubility and stability. Prepare each according to its own product page rather than carrying assumptions across.
What do the current certificates show?
Pharmacology decides which compound answers the question; the certificate decides what is actually in the vial. These are the current lots for each, read from the certificate library:
| Compound | Lot | Identity | Purity | Content | Issued |
|---|---|---|---|---|---|
| Ipamorelin | IPA5-0803 | LC-MS/MS | 99.78% | 5.17 mg vs 5 mg label | Aug 17, 2026 |
| Sermorelin | SERMO5-0318 | MALDI-MS | 99.8% | 6.36 mg vs 5 mg label | Apr 3, 2026 |
Purity on both lines is area percent by RP-HPLC at 214 nm, which the area-percent post explains is a ratio of peak areas and not a weight, so the two figures are comparable only because the method is the same. Content is the measured mass against the label, and the lot-to-lot post is the case for using it rather than the label in any calculation. All 114 certificates read together are in the certificate dataset.
Common questions
Which clears faster?
Sermorelin clears fastest of the GHRH analogues in this catalogue, which is why it is used where a pulse rather than a plateau is wanted.
Are they ever used together?
Yes, in designs that engage both receptors at once. The growth-hormone-axis category lists the blends built for that.
Where to go next
- Ipamorelin research guide · Ipamorelin product page
- Sermorelin research guide · Sermorelin product page
For laboratory research use only. Clinical trial results are cited as context and do not describe use of the material sold here.