Buying Sermorelin in the USA: the Unmodified Reference Analog
Take growth hormone-releasing hormone and cut it back as far as full receptor activity allows, and you arrive at sermorelin, essentially unmodified. Those two attributes together make it the family’s reference compound: each engineered GHRH analog amounts to an answer to a problem that sermorelin has and leaves unsolved.
Coupling, and picking the readout
A class B GPCR, the GHRH receptor sits structurally alongside those for secretin, glucagon and the incretins. Coupling runs through Gαs, activating adenylate cyclase and driving intracellular cAMP upward.
Assay selection follows from that, and this is where designs most often fail by analogy. Default to a cAMP accumulation assay. Calcium flux, the correct instrument for a Gαq-coupled receptor like KISS1R (see kisspeptin-10 and KISS1R signaling), is the wrong instrument for GHRHR, and a weak or absent calcium response tells you nothing about whether the compound is active.
Indexed literature sits at PubMed, alongside the broader GHRH receptor structure-activity literature.
Where the protease cuts
Tyr-Ala opens the GHRH sequence, and dipeptidyl peptidase-4 strips N-terminal dipeptides whose second residue is alanine or proline. Presenting exactly that motif, GHRH(1-29) gets cut by DPP-4 between Ala2 and Asp3, leaving a GHRH(3-29) stripped of the receptor-binding determinants at its N-terminus.
Everything in the design space around this molecule follows from that one vulnerability. Tesamorelin hangs a trans-3-hexenoyl group off the N-terminus, leaving the protease nothing to grip. CJC-1295 swaps residues within the cleavage region and, in its DAC form, carries a group that binds serum albumin; see the difference between the DAC and no-DAC forms. One question, different answers, with sermorelin standing as the unanswered version.
At the bench the implication is plain: wherever DPP-4 activity is present in a preparation, sermorelin is being consumed as the experiment proceeds. That belongs to the molecule rather than to any defect in the material, and no certificate is going to mention it.
Twenty-nine residues, and a tail that does nothing
Native GHRH extends to 44 residues. Sermorelin takes the first 29 of them and carries a C-terminal amide, written GHRH(1-29)-NH2. Nothing in residues 30 through 44 contributes to receptor activation, which is how truncation at 29 became the standard economy and why several analogs are built on that same fragment.
Separating sermorelin from those analogs is the list of things that have not been done to it: no acylation, no substituted residue, no albumin-binding group. Just the parent pharmacophore minus the redundant tail.
An amidation you cannot see
Full activity at the GHRH receptor requires the C-terminal amide. Lose or omit it and the corresponding free acid results, substantially less potent than the amidated form.
It also hides well. Roughly one dalton separates amide from free acid, they behave almost identically on a reversed-phase column, and in the vial they look the same. Mass spectrometry resolves them, though only when somebody asks the question deliberately. So when reading a certificate, confirm the calculated mass quoted is the one for the amidated form. Fields on the document are covered in our guide to reading a certificate of analysis, and what each technique can resolve is explained in how purity and identity are verified.
When the unmodified compound is the better tool
A short lifetime makes sermorelin easy to file away as the family’s weakest member. That framing is wrong often enough to be worth correcting.
Signaling at the GHRH receptor is pulsatile. A stabilized analog delivering extended exposure is not a longer-lasting version of the native signal but a different signal altogether, and receptors that desensitize under sustained stimulation will behave accordingly. Where the question concerns transient, native-like receptor engagement, the unmodified fragment is the faithful tool and the long-acting analog becomes the confound.
From which comes the design error this family invites, namely treating GHRH analogs as interchangeable. Protocols written around sermorelin do not transfer to tesamorelin or to CJC-1295 with DAC, and results from one should not be pooled with results from another. How the two mechanisms differ is set out in our comparison of GHRH analogs against growth hormone secretagogues, while the chemistry behind the modifications appears in peptide half-life and how analogs extend it.
At the bench
Shipped as lyophilized powder, sermorelin is stable in that state while it stays sealed, cold and dry. Risks are ordinary for a peptide of this length, and three are worth naming individually.
| Risk | What to do about it |
|---|---|
| Moisture | Bring the vial to room temperature before the seal is broken. Open a cold vial into a warm room and water condenses directly onto the cake, and water is what drives hydrolysis along with the deamidation of asparagine and glutamine during storage. See storage and stability. |
| Aggregation in solution | Genuine helical propensity in a 29-residue peptide means it aggregates more readily than a short linear one, and repeated freeze-thaw accelerates this by way of the ice interface rather than heat. Reconstitute once and split into single-use volumes before freezing, so that every later thaw is a first thaw for that aliquot. See aliquoting reconstituted peptides. |
| Gross weight on the label | As with any synthetic peptide, the milligram figure is gross. Counter-ion and residual water form part of that mass without forming part of the peptide, so molarity read off the label is overstated. See net peptide content explained. |
Products
Sermorelin 5mg and Sermorelin 10mg, listed with other growth hormone pathway compounds. The third-party reports we have obtained are published on our certificates of analysis page.
ExoLabz supplies compounds for laboratory research use only. Nothing on this page is medical advice or a suggestion of human or veterinary use. These compounds hold no FDA approval for human use.
Compare sermorelin with tesamorelin and CJC-1295 (no DAC) on one page: sermorelin vs tesamorelin vs CJC-1295.