Sermorelin: Why 29 of GHRH's 44 Residues Are Enough

For laboratory research use only. Not for human or veterinary use.

Sermorelin is the first 29 residues of growth hormone-releasing hormone (GHRH), made synthetically, with nothing changed. It is the parent of the modern GHRH analogues, CJC-1295 among them, and unlike most compounds in a research catalogue it was once a licensed medicine in the United States. This guide sets out what sermorelin is, why 29 residues were chosen, the one weakness every later analogue was built to fix, what the human research covers, and what to check on a certificate.

Identity#

The masses are our own calculation from the sequence. Three features matter later: alanine at position 2, where the peptide is cut in plasma; a single methionine at position 27, which oxidises; and an amidated end, which is part of the molecule rather than a detail.

Where the 29 came from#

GHRH itself is 44 residues long. It was first isolated in 1982, by Roger Guillemin’s group, from a pancreatic tumour that was producing it in quantity; the same sequence was then confirmed in the human hypothalamus, where it is normally made.

Two years later the same group asked how much of it was needed. In a 1984 study they made a series of shortened versions, trimming residues from the end, and tested each one on cultured rat pituitary cells. Trimming down to 34 residues cut the potency to about a quarter of the full peptide. But the 31-, 30- and 29-residue fragments all came back at about half, so going further did not cost anything more. Below that, potency fell away steeply, and at 19 residues the activity disappeared completely.

So “29 is enough” is a practical statement rather than an exact one. GRF(1-29) is the shortest fragment that keeps a large share of the potency, and a 29-residue peptide is far cheaper and simpler to make than a 44-residue one. It is often described as the shortest fragment with full biological activity, which is true of what it can do rather than how strongly it does it in that assay.

The weakness: position 2#

Natural GHRH is broken down very quickly. In 1986, Lawrence Frohman and colleagues showed that an enzyme in plasma cuts the first two residues off the front. In volunteers given the full peptide into a vein, its half-life was 6.8 minutes, and the shortened product had less than a thousandth of the original activity. The enzyme is now known as DPP-4.

Sermorelin keeps the natural alanine at position 2, so it has exactly the same weakness. Anti-doping researchers detected the shortened form, GHRH(3-29), in human plasma after sermorelin was given. Almost every GHRH analogue since has been designed around this one point: CJC-1295 replaces that alanine with its mirror-image form, which the enzyme cannot cut. Our CJC-1295 guide sets out the four substitutions and what each is for.

A licensed medicine, once#

Sermorelin was developed by Serono under the name Geref. The US Food and Drug Administration approved a diagnostic form in 1990 and a second form in 1997. Serono discontinued both in 2008, and in 2013 the FDA formally determined that neither had been withdrawn from sale for reasons of safety or effectiveness (Federal Register notice).

That history is the reason sermorelin has more human data than most research peptides. It is not sold as a licensed medicine in the US today.

What the human research covers#

Most of it dates from the late 1980s and the 1990s, and the studies are small.

• The licensed-use data. A 1999 review summarised the evidence behind Geref’s approvals: its use as a test of pituitary growth hormone release, and a limited set of trials of daily administration over periods of up to three years.
• 1992, healthy older men. Ten men averaging 68 years old were compared with nine young men, and the older group then received GRF(1-29) twice a day for 14 days at two levels, in random order. At the higher level, average growth hormone and IGF-1 rose to the values seen in the young men. At the lower level the changes were not significant.
• 1997, the same question taken further. Eleven healthy men aged 64 to 76 received it once each night for six weeks, with no placebo group. Night-time growth hormone release rose, but IGF-1 did not change, and neither did body composition measured by DEXA. The authors concluded that a single nightly administration was less effective than several a day.

Read together, those two studies are a fair picture of the compound: a clear effect on growth hormone release, an effect on IGF-1 that depended on how often it was given, and nothing larger demonstrated. The short half-life explains the pattern.

Anti-doping status#

GHRH and its analogues, sermorelin included, are on the World Anti-Doping Agency Prohibited List, and anti-doping laboratories have published methods for detecting sermorelin and its breakdown product in plasma. Anyone subject to anti-doping testing should not handle it. As with CJC-1295 and ipamorelin, this is a plain fact about the compound and belongs on the page.

What to check on the certificate#

• Mass: 3357.9 (monoisotopic 3355.82). On a mass spectrum, expect charged ions near 1119.6 (triply charged), 840.0 (quadruply) and 672.2 (five charges).
• Not modified GRF(1-29). CJC-1295 without DAC is the same fragment with four substitutions, at 3367.9, only 10 units heavier. Its triply charged ion sits at 1123.0. A certificate that rounds to “about 3360” cannot tell the two apart.
• Methionine oxidation. Oxidised sermorelin is 16 heavier, at 3373.9. Its triply charged ion lands near 1125.0, close to modified GRF’s, so the instrument’s resolution and the full mass both matter.
• Amide, not acid. The free-acid version, with the same sequence but no amide, is 1 unit heavier at 3358.9. The 1984 study made both. A certificate should state the amide.
• The cut product. A peak near 3123.6 is GHRH(3-29): material that has already lost its first two residues.
• Net peptide content and counter-ion. With five basic residues (three arginines, two lysines) plus the free amino end, sermorelin can carry up to six counter-ions, here acetate. Net peptide content is how much of the powder is peptide, and it is not the same number as purity.
• Purity, with the method named, measured on that batch.

Ask about the documentation for the batch we would ship before you order. See also how to read a COA, how much is actually in the vial and what a purity figure means.

Handling and storage#

Standard peptide handling applies, with some extra care over air because of the methionine. Store the sealed lyophilised vial cold, dry and out of light, and let it reach room temperature before opening so moisture does not condense inside. Reconstitute by running bacteriostatic or sterile water down the vial wall rather than onto the powder, and swirl rather than shake. Once in solution, keep it refrigerated. The reconstitution guide, solvent guide and storage guide cover the detail.

What Pioneer supplies#

Sermorelin acetate is stocked in a 10mg vial, with 2mg and 5mg vials made to order in one to two weeks. We also stock both forms of its best-known descendant: CJC-1295 without DAC and CJC-1295 with DAC.

Quality comes first#

Sermorelin sits 10 mass units from its most common relative, 1 unit from its own free-acid version, and 16 from its oxidised form, and the enzyme that limits it in plasma leaves a fragment of its own. The mass on the certificate is what separates all of these. Ask about the documentation for the batch we would ship before you order.

Sources#

Each entry links to its PubMed record, where the title and abstract can be read. The descriptions are ours: they say what each paper examined, not what it is claimed to show. Records checked on PubMed on 1 November 2026.

1. Guillemin R, Brazeau P, Böhlen P, et al. (1982). Science 218(4572):585–7. The first isolation and sequence of the 44-residue growth hormone-releasing factor, from a human pancreatic tumour. PubMed 6812220
2. Ling N, Baird A, Wehrenberg WB, et al. (1984). Biochem Biophys Res Commun 123(2):854–61. Shortened versions of the 44-residue peptide, amide and free acid, tested on rat pituitary cells to find how much of the sequence is needed. PubMed 6435620
3. Frohman LA, Downs TR, Williams TC, et al. (1986). J Clin Invest 78(4):906–13. Breakdown of natural GHRH in human plasma and in volunteers: removal of the first two residues by a plasma enzyme, and the activity of the shortened product. PubMed 3093533
4. Corpas E, Harman SM, Piñeyro MA, et al. (1992). J Clin Endocrinol Metab 75(2):530–5. Ten healthy older men given GRF(1-29) twice a day for 14 days at two levels, compared with nine young men, measuring growth hormone and IGF-1. PubMed 1379256
5. Vittone J, Blackman MR, Busby-Whitehead J, et al. (1997). Metabolism 46(1):89–96. Eleven healthy men aged 64 to 76 given GRF(1-29) nightly for six weeks, measuring growth hormone, IGF-1, body composition and muscle function. No placebo group. PubMed 9005976
6. Prakash A, Goa KL. (1999). BioDrugs 12(2):139–57. Review of the evidence behind sermorelin's licensed uses as Geref. PubMed 18031173
7. Knoop A, Thomas A, Fichant E, et al. (2016). Anal Bioanal Chem 408(12):3145–53. A validated anti-doping method for detecting several GHRH analogues in plasma, including sermorelin and its shortened form GHRH(3-29). PubMed 26879649

In our catalogue#

• Sermorelin Acetate — 10mg in stock; 2mg and 5mg made to order
• CJC-1295 (without DAC) — modified GRF(1-29), the four-substitution descendant
• CJC-1295 (with DAC) — the albumin-binding form

Pioneer Research Peptides — UK supplier of research peptides for laboratory use. Ask about batch documentation before you order.

For laboratory research use only — not for human consumption. 18+.