Quick answer
Sermorelin is a synthetic 29-residue, C-terminally amidated peptide that reproduces the N-terminal fragment of human growth-hormone-releasing hormone (GHRH 1–29), the shortest segment that keeps full activity at the GHRH receptor. It is used in the laboratory as an unmodified reference agonist of the Gs-coupled GHRH receptor on pituitary somatotrophs, and as the baseline against which stabilized analogs such as tesamorelin and CJC-1295 are compared.
- Identity: GHRH(1–29)-NH2, theoretical average mass about 3,358 Da
- Pathway: GHRH receptor → Gs → adenylyl cyclase → cAMP → GH synthesis and release in model systems
- Handling weak points: methionine at position 27 (oxidation), asparagine at position 8 (deamidation), and rapid proteolysis in serum-containing media
- Bench math: mg in vial ÷ mL of diluent = mg/mL; the reconstitution calculator does it for any vial
For laboratory research use only; not for human consumption. This guide collects the structure, history, signaling biology, preclinical model systems and handling chemistry of sermorelin in one place, so that researchers can design experiments around what the molecule actually is. Research-grade material is listed on the sermorelin product page.
What sermorelin is
Sermorelin is a synthetic analog that corresponds to the first 29 amino acids of human growth-hormone-releasing hormone, a 44-residue peptide made in the hypothalamus. Its sequence is Tyr-Ala-Asp-Ala-Ile-Phe-Thr-Asn-Ser-Tyr-Arg-Lys-Val-Leu-Gly-Gln-Leu-Ser-Ala-Arg-Lys-Leu-Leu-Gln-Asp-Ile-Met-Ser-Arg, with an amide group on the C-terminal arginine. Because it carries no substitutions, no acyl group and no albumin-binding handle, it is effectively the native hormone core, trimmed to the portion needed to activate the receptor.
In research it plays three roles. First, it is a tool for asking whether a pituitary preparation or receptor-expressing cell line still signals through the GHRH receptor. Second, it is an upstream probe: it acts at the releasing-hormone receptor rather than mimicking growth hormone itself, so readouts sit one step earlier in the axis than they would with a growth hormone preparation. Third, and most commonly in current literature, it is the unmodified comparator for newer GHRH analogs. Equal nominal concentrations of different analogs do not guarantee equal intact-peptide exposure, and sermorelin, being the least protected member of the family, shows how much of a difference between analogs is due to persistence rather than receptor potency.
| Property | Sermorelin |
|---|---|
| Parent molecule | Human GHRH, 44 residues |
| Length of sermorelin | 29 residues, GHRH(1–29) |
| C-terminus | Amidated |
| Theoretical average mass | About 3,358 Da |
| Receptor | GHRH receptor (class B G-protein-coupled receptor, Gs-coupled) |
| Modifications | None; native sequence |
| Known chemical liabilities | Met27 oxidation; Asn8 deamidation; N-terminal dipeptide cleavage by dipeptidyl peptidase-4 |
| Supplied form | Lyophilized powder |
Discovery and history
Characterizing GHRH
The hypothalamic signal that drives pituitary growth hormone release was sought for decades before it was isolated. The decisive step came in 1982, when groups led by Roger Guillemin and by Jean Rivier and Wylie Vale independently isolated and sequenced a growth-hormone-releasing factor from pancreatic islet tumors associated with excess growth hormone secretion. The hypothalamic form, a 44-residue peptide, was then isolated and sequenced and shown to match the tumor-derived factor. Having the sequence meant that structure-activity questions could finally be asked directly.
From the full hormone to a minimal fragment
Structure-activity work established that GHRH(1–29) retained the receptor activity of the full hormone, making it the shortest fragment with full activity. That finding turned a long hormone into a compact, cheaper-to-synthesize research reagent, and the fragment became known as sermorelin. The practical consequence for chemists was significant: a 29-residue chain is far more tractable by solid-phase synthesis than a 44-residue chain, and it concentrated attention on the N-terminal region that governs receptor activation. The sequence logic is explained in understanding amino acid sequences.
A template for later analogs
The GHRH(1–29) scaffold became the starting point for more stable analogs. Substituted 29-residue variants such as CJC-1295 (no DAC) block the protease-sensitive N-terminus with amino acid changes, while the DAC-bearing form adds an albumin-reactive group, described in the CJC-1295 DAC overview. Tesamorelin took a different route, keeping all 44 residues and capping the N-terminus with an acyl group; see the tesamorelin overview. A key early observation behind all of these programs was that plasma rapidly degrades GHRH to an inactive N-terminally truncated product, work associated with Frohman and colleagues in the mid-1980s. Stabilization was therefore the central engineering question, and sermorelin supplied the unprotected reference point.
Changing terminology
Older papers may use GHRH, GRF or somatocrinin for closely related concepts. Careful reading requires attention to species, fragment boundaries and terminal modifications; a shared label alone does not prove that two preparations are chemically identical, which is why sequence-level reporting matters when old and modern experiments are compared. The distinction between discovery and optimization also matters: sermorelin showed that the native fragment is active, while the later analogs asked how substitution or conjugation changes stability without losing receptor recognition. See also the standalone discovery and history article.
Chemical structure and synthesis
Sequence and mass
Sermorelin is a linear peptide with no cysteine, so there are no disulfide bridges to form, reduce or mis-pair. This simplifies both synthesis and analysis compared with disulfide-containing peptides. It contains one methionine (position 27) and one asparagine (position 8) that sits in a motif prone to deamidation, and its basic residues (arginine and lysine at several positions) make it readily soluble in water.
Solid-phase assembly
Like most research peptides of this length, sermorelin is built by solid-phase peptide synthesis: the chain is assembled residue by residue on a resin support, cleaved from the resin with side-chain deprotection, purified by reversed-phase chromatography and lyophilized. The drying step is discussed in what is lyophilization. At 29 residues the chain is long enough that truncated and deletion sequences can accumulate during coupling cycles, so purification is what separates the intact full-length peptide from near-identical impurities.
Why a single mass value is not enough
A mass spectrum confirms overall composition but may not resolve every positional or sequence-related impurity. A fuller material profile combines chromatographic purity, mass analysis, peptide content, counterion information and residual moisture. Reference standards and system-suitability checks show whether a method separates the intact chain from nearby impurities. Lot comparisons should use identical chromatographic conditions, because purity percentages produced with different gradients, wavelengths or integration rules are not automatically equivalent. The distinction between the two main techniques is covered in HPLC versus mass spectrometry.
Where sermorelin sits among GHRH analogs
| Analog | Design | Approx. mass | Stabilization strategy |
|---|---|---|---|
| Sermorelin | GHRH(1–29) amide, unmodified | 3,358 Da | None; shortest persistence |
| CJC-1295 (no DAC) | GHRH(1–29) with four substitutions | 3,368 Da | Residue substitutions that resist cleavage |
| CJC-1295 (DAC) | Substituted fragment plus albumin-reactive group | 3,647 Da | Albumin coupling; longest persistence |
| Tesamorelin | GHRH(1–44) amide with N-terminal trans-3-hexenoyl group | 5,136 Da | N-terminal acyl cap on full-length chain |
Mechanism of action
Receptor engagement and the cAMP pathway
Sermorelin presents the active GHRH(1–29) sequence to the GHRH receptor on pituitary somatotroph cells. The receptor couples to Gs, activating adenylyl cyclase and raising intracellular cyclic AMP. Elevated cAMP activates protein kinase A, which in model systems promotes both release of stored growth hormone and transcription of the growth hormone gene. This is the same second-messenger logic seen across many class B GPCR studies. The structural basis of engagement is outlined in the chemistry article.
Upstream position in the axis
Because sermorelin acts at the releasing-hormone receptor, the signal it generates is upstream of growth hormone itself. That matters when reading data: a growth hormone release readout reflects the integrated state of the somatotroph, including its stores, its receptor density and the opposing influence of somatostatin, which inhibits the same cells. Many protocols examine the two signals together for this reason.
Contrast with ghrelin-receptor secretagogues
Ghrelin-mimetic secretagogues such as ipamorelin act at the GH-secretagogue receptor, a different receptor with different signaling. Running the two classes side by side is a standard way to dissect the two arms of the growth-hormone axis; see ipamorelin’s mechanism and the sermorelin versus ipamorelin comparison. Comparisons with longer-lived GHRH analogs, by contrast, separate receptor engagement from pharmacokinetics, since those analogs share the same receptor but differ in duration.
Preclinical research findings
Preclinical work on sermorelin centers on how the GHRH(1–29) fragment engages its receptor and prompts pulsatile signaling in pituitary preparations. Isolated pituitary cultures and rodent models have historically been the main substrates, because they let investigators observe release dynamics under controlled conditions rather than in whole organisms. The table lists the systems in regular use and what each contributes.
| Model system | Typical readout | What it contributes |
|---|---|---|
| Primary rat anterior pituitary cells | GH released into medium versus concentration and time | Direct measure of somatotroph responsiveness; omits hypothalamic and peripheral feedback |
| Perifused pituitary preparations | GH release under continuous flow | Captures release dynamics and desensitization during sustained versus pulsed stimulation |
| Receptor-expressing cell lines | cAMP accumulation | Clean, receptor-level measure of GHRH-receptor activation |
| Rodent models | Plasma GH profiles | Whole-animal context; strains with GHRH-receptor mutations serve as negative controls |
| Serum-containing media or plasma | Intact peptide over time | Tracks proteolytic loss, notably the N-terminal dipeptide cleavage by dipeptidyl peptidase-4 |
Pulsatility and desensitization
A long-standing question is how somatotrophs respond to continuous versus intermittent GHRH-receptor stimulation. In perifusion experiments, sustained exposure leads to a declining growth hormone response, attributed to receptor desensitization and depletion of releasable stores, while pulsed exposure preserves responsiveness. Because sermorelin is short-lived, it suits protocols that need a defined, brief stimulus followed by recovery. Longer-acting analogs are the natural choice when the question concerns prolonged receptor occupancy.
Stability as the main confounder
Unmodified GHRH(1–29) is cleaved by dipeptidyl peptidase-4, which removes the first two residues and yields an inactive product, and it persists for only minutes in plasma. Substituted analogs block this cleavage, and tesamorelin reaches a similar end with an N-terminal acyl group. Running sermorelin next to such analogs shows how much of any difference arises from persistence and how much from receptor activity. The comparison logic is developed in the tesamorelin versus sermorelin comparison and in the preclinical research article.
Handling, reconstitution and storage
Sermorelin has the native sequence, including a methionine at position 27 and residues prone to deamidation, so it is less resistant to degradation than the modified analogs. Handling time at room temperature should be kept short and cold, dark storage is the default. The concentration relationship is simply mg of peptide divided by mL of diluent; use the peptide calculator for any vial size. The standalone sermorelin reconstitution and storage article gives the short version, and the general technique is in the lyophilized-peptide reconstitution guide. A fully worked bench protocol for another peptide, with the same step order, is in the retatrutide reconstitution walkthrough; the technique transfers even though the peptide differs.
Preparation principles
- Let the sealed vial reach room temperature before opening so condensation does not wet the cake.
- Add bacteriostatic water slowly down the inside wall of the vial, not onto the powder.
- Dissolve by gentle swirling. Do not vortex or shake: foam and air–liquid interfaces promote aggregation and expose Met27 to oxygen.
- The solution should be clear and colorless. Haze or particles mean it should not be used for quantitative work.
- Label with date, diluent, volume and mg/mL at the time of preparation.
Illustrative concentration table
The table shows a hypothetical 5 mg vial of lyophilized sermorelin (average mass about 3,358 g/mol) reconstituted in different volumes, with the matching molar concentration before correcting for net peptide content. Check the batch certificate for peptide content before quantitative work.
| Diluent added | Concentration | Molar concentration |
|---|---|---|
| 1 mL | 5 mg/mL | 1,489 µM |
| 2 mL | 2.5 mg/mL | 745 µM |
| 2.5 mL | 2 mg/mL | 596 µM |
| 5 mL | 1 mg/mL | 298 µM |
Storage
The lyophilized powder is the most stable form; keep it cold, dry and away from light. Native-sequence GHRH fragments degrade comparatively quickly in solution, so the standard answer is to make up only what is needed and to freeze single-use aliquots in low-binding tubes promptly, thawing each once. Reconstituted stock kept at 2–8 °C and protected from light should be treated as short-term material; the commonly quoted 28-day figure for preserved multi-use containers comes from sterility standards, not from a sermorelin-specific stability study, and is a ceiling rather than a shelf life. Both known chemical liabilities, Met27 oxidation and Asn8 deamidation, are slowed by cold temperatures, limited headspace exchange and minimal freeze–thaw cycling. Fresh solutions are best for sensitive receptor assays. General cold-chain principles are in storing research peptides.
| Condition | Guidance | Reason |
|---|---|---|
| Lyophilized, sealed | Cold, dry, dark | Dry state is the most robust form |
| Reconstituted, 2–8 °C | Short-term; keep dark | Deamidation and oxidation proceed in solution |
| Single-use aliquots, frozen | Thaw once | Avoids ice-interface stress from repeat cycles |
| Bench, room temperature | Minimize time | Highest rate of chemical and enzymatic loss |
Purity, COA and quality
For a 29-residue peptide, deletion and truncation sequences are the main impurity class, and oxidized or deamidated variants form during storage. A useful routine before a lot enters an experiment: confirm that the batch number on the vial appears on the certificate of analysis; look at the chromatogram itself, not just the summary percentage; confirm the measured mass matches the theoretical mass; and log batch, storage history and preparation date alongside the data. This turns the reagent into a documented variable, which is what reviewers and collaborators need in order to reproduce a result. Batch documents are published on the CoA page, and reading them is explained in how to read a COA and understanding HPLC purity. Lot-level analysis specific to this peptide is described in sermorelin purity testing and identity verification. For sourcing criteria, see where to buy sermorelin for research, and for the material itself the sermorelin research vials.
Related compounds and comparisons
- Tesamorelin: full-length GHRH(1–44) with an N-terminal acyl cap; compared directly in tesamorelin versus sermorelin.
- Ipamorelin: a ghrelin-receptor secretagogue acting through a separate receptor; see sermorelin versus ipamorelin and the ipamorelin overview.
- CJC-1295 (no DAC) and CJC-1295 (DAC): stabilized GHRH(1–29)-derived analogs, covered in their no-DAC and DAC overviews.
Stabilized analogs are available as CJC-1295 (no DAC) and tesamorelin research material. Whichever analog is chosen, state clearly whether the experiment tests receptor potency or persistence, because the same nominal concentration of each peptide will not deliver the same amount of intact molecule over time.
Frequently asked questions
What is sermorelin in structural terms?
The first 29 residues of human growth-hormone-releasing hormone with a C-terminal amide. It is the shortest GHRH fragment shown to retain full receptor activity, with a theoretical average mass of about 3,358 Da.
Which receptor does sermorelin act on?
The GHRH receptor, a class B G-protein-coupled receptor on pituitary somatotrophs. It couples to Gs, which raises intracellular cAMP and activates protein kinase A in model systems.
How does sermorelin differ from ipamorelin?
They act at different receptors. Sermorelin is a GHRH-receptor agonist, while ipamorelin acts at the ghrelin/GH-secretagogue receptor. The two are often compared in the same assay to separate the two arms of the growth-hormone axis.
Why is sermorelin used as a baseline comparator?
It has the native sequence with no stabilizing changes, so it represents unmodified GHRH-receptor agonism. Stabilized analogs such as tesamorelin and CJC-1295 are measured against it to separate persistence from receptor potency.
Why does sermorelin persist for such a short time in serum-containing media?
Dipeptidyl peptidase-4 removes the N-terminal dipeptide, producing an inactive fragment, and other peptidases contribute. This rapid loss is what motivated the stabilized analogs.
Which readouts are standard in GHRH-analog cell studies?
cAMP accumulation in receptor-expressing cells and growth hormone release from primary pituitary cultures, usually across a concentration series and often with somatostatin as a counter-regulatory control.
What are sermorelin's main chemical liabilities?
Methionine at position 27 can oxidize to its sulfoxide, and asparagine at position 8 can deamidate in solution. Cold storage, limited air exposure, fresh solutions and few freeze–thaw cycles reduce both.
How is the concentration of a reconstituted vial calculated?
Divide the mass of peptide in the vial by the volume of diluent added. A 5 mg vial in 2 mL gives 2.5 mg/mL, about 744 µM at a mass of 3,358 g/mol, before correcting for net peptide content on the certificate of analysis.
What documentation should accompany a sermorelin lot?
A lot-specific certificate of analysis showing HPLC purity with the chromatogram and mass-spectrometry identity near the theoretical mass, matched to the batch number on the vial.
Can results from pituitary cell assays be generalized?
Only cautiously. Dispersed cells omit hypothalamic and peripheral feedback, and potency varies with cell type, medium and peptide stability, so findings describe the tested system rather than any whole-organism outcome.
Research-use statement
Sermorelin is supplied strictly as a laboratory reagent. For laboratory research use only; not for human consumption. Nothing in this guide is usage guidance; concentrations given are bench stock arithmetic for in-vitro work, and the findings described come from isolated cells, tissue preparations and animal models. Material is also not intended for veterinary or diagnostic purposes. See the product page for supply information.
References
- Guillemin R, Brazeau P, Böhlen P, Esch F, Ling N, Wehrenberg WB. Growth hormone-releasing factor from a human pancreatic tumor that caused acromegaly. Science. 1982;218(4572):585-587.
- Rivier J, Spiess J, Thorner M, Vale W. Characterization of a growth hormone-releasing factor from a human pancreatic islet tumour. Nature. 1982;300(5889):276-278.
- Ling N, Esch F, Böhlen P, Brazeau P, Wehrenberg WB, Guillemin R. Isolation, primary structure, and synthesis of human hypothalamic somatocrinin: growth hormone-releasing factor. Proc Natl Acad Sci USA. 1984;81(14):4302-4306.
- Frohman LA, Downs TR, Williams TC, Heimer EP, Pan YC, Felix AM. Rapid enzymatic degradation of growth hormone-releasing hormone by plasma in vitro and in vivo to a biologically inactive product cleaved at the Tyr1-Ala2 bond. J Clin Invest. 1986;78(4):906-913.
- Manning MC, Chou DK, Murphy BM, Payne RW, Katayama DS. Stability of protein pharmaceuticals: an update. Pharm Res. 2010;27(4):544-575.
- Wang W. Lyophilization and development of solid protein pharmaceuticals. Int J Pharm. 2000;203(1-2):1-60.
- Goebel-Stengel M, Stengel A, Taché Y, Reeve JR Jr. The importance of using the optimal plasticware and glassware in studies involving peptides. Anal Biochem. 2011;414(1):38-46.