Sermorelin (GHRH 1–29): A Research Review of the Reference GHRH Analog and How It Differs from Mod GRF 1–29, CJC-1295 and Tesamorelin

By Peptide Insider Research Team · 11 min read · Last updated 2026-09-06

Sermorelin (GHRH 1–29, formerly marketed as Geref) is the shortest fragment of human growth hormone–releasing hormone that retains the full receptor activity of the 44–amino-acid parent peptide. Because it works upstream of the pituitary — stimulating the gland's own pulsatile growth-hormone output rather than supplying the hormone — it has served for four decades as the reference GHRH analog against which longer-acting derivatives such as Mod GRF 1–29, CJC-1295 and tesamorelin are compared. This review covers its structure, mechanism, the published clinical and preclinical evidence, and the frequently confused naming around “CJC-1295 without DAC.” All content is provided strictly for research reference and is not intended for human or veterinary use.

Sermorelin at a glance

Attribute	Detail
Compound class	GHRH analog (GHRH-receptor agonist); GH secretagogue
Sequence	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-NH2 (human GHRH 1–29 amide) [1,6]
Length / mass	29 residues; ~3,358 Da (free peptide); typically supplied as sermorelin acetate
Primary target	Pituitary GHRH receptor (class B GPCR, Gs/cAMP/PKA) [4]
Circulating half-life	Approximately 10–20 minutes; degraded by DPP-4 and trypsin-like proteases [6]
Regulatory history	Approved in the US in 1997 (Geref) for pediatric diagnostic and therapeutic use; withdrawn from the market by the manufacturer in 2008 for commercial reasons [2,3]
Frequently confused with	Mod GRF 1–29 (“CJC-1295 without DAC”), CJC-1295 with DAC, tesamorelin

Introduction

Human GHRH was isolated and sequenced in 1982–1984, first from pancreatic tumors causing acromegaly and then from hypothalamic tissue, where it was shown to be a 44-residue amidated peptide [1]. Structure–activity work quickly established that the biological activity resides in the N-terminal 29 residues: GHRH(1–29)-NH₂ stimulated growth hormone (GH) release from pituitary cells with potency indistinguishable from the full-length hormone, while shorter fragments lost activity [2]. That 29-residue fragment, given the nonproprietary name sermorelin, became a licensed diagnostic agent and a pediatric therapy under the brand Geref and, more durably, a laboratory standard for probing the somatotropic axis [2,3].

Sermorelin's research interest today is threefold. It is the parent scaffold from which the stabilized analogs Mod GRF 1–29, CJC-1295 and tesamorelin were derived, making it the natural comparator in secretagogue pharmacology [7,8]. It has an unusually long human clinical record, including six- and twelve-month studies in older adults that measured GH pulsatility, IGF-1, body composition, sleep and cognition [9,10,11]. And its extremely short half-life makes it a useful tool for asking how the pattern — rather than the amount — of GH release shapes downstream physiology [4,6].

The GHRH–GH–IGF-1 axis

GH secretion from anterior-pituitary somatotrophs is controlled by two hypothalamic peptides acting in opposition: GHRH, which stimulates synthesis and release, and somatostatin, which inhibits release without blocking synthesis. Their alternating output produces the pulsatile GH pattern seen in all mammals, with the largest pulses occurring in early slow-wave sleep [4,5]. A third input, the gastric peptide ghrelin, acts at a separate receptor (GHS-R1a) and amplifies GHRH-driven pulses; this is the receptor targeted by GHRP-6, ipamorelin and related ghrelin mimetics rather than by GHRH analogs [5].

Circulating GH acts on the liver and peripheral tissues to induce insulin-like growth factor 1 (IGF-1), which mediates many of GH's anabolic effects and closes the loop by inhibiting GHRH neurons and stimulating somatostatin release [4]. With advancing age, GHRH pulse amplitude declines and somatostatin tone increases, producing the roughly 50% fall in 24-hour GH output between young adulthood and the seventh decade that the literature terms “somatopause” [9,11]. Because the pituitary itself remains responsive, this pattern is the rationale for studying GHRH analogs — they test whether restoring the upstream signal can normalize downstream hormone levels while leaving negative feedback intact [9,10].

Structure and mechanism of action

Sermorelin is chemically identical to native GHRH residues 1–29 with a C-terminal amide; there are no non-natural substitutions [2]. Receptor binding depends on the N-terminal Tyr¹-Ala²-Asp³ motif and on an amphipathic α-helix spanning roughly residues 6–29, which docks into the extracellular domain of GHRH-R, a class B (secretin-family) G-protein-coupled receptor expressed almost exclusively on somatotrophs [4]. Agonist binding activates G_s, raising cAMP and activating protein kinase A; PKA phosphorylates CREB, driving transcription of the GH gene and of the Pit-1 transcription factor, and also promotes calcium influx through L-type channels that triggers exocytosis of GH-containing granules [4]. GHRH therefore both releases stored GH within minutes and replenishes the releasable pool over hours — a dual action that ghrelin mimetics lack.

The compound's defining pharmacokinetic feature is instability. Frohman and colleagues demonstrated in 1989 that human plasma DPP-4 cleaves GHRH between Ala² and Asp³ within minutes, producing the inactive (3–44) or (3–29) metabolite, with a secondary trypsin-like cleavage at Arg¹¹–Lys¹² [6]. Sermorelin shares this liability, and the reported half-life of 10–20 minutes means a single exposure produces one physiological GH pulse rather than sustained elevation [3,6]. Every later analog is an attempt to engineer around this: D-Ala² blocks DPP-4, Gln⁸ and Ala¹⁵ reduce asparagine deamidation and oxidation, Leu²⁷ replaces the oxidation-prone methionine, and in tesamorelin an N-terminal trans-3-hexenoyl group performs the DPP-4-blocking role instead [7,8].

Evidence by research domain

Research domain	Typical models	Reported findings	Evidence maturity
GH/IGF-1 axis restoration in aging	Healthy older men and women, 2–12 months	Increased GH pulse amplitude and IGF-1 toward young-adult reference range with preserved pulsatility [9,10,11]	Multiple controlled clinical studies
Body composition	Older adults, DEXA/anthropometry	Modest increases in lean mass, reduced abdominal skinfold; outcomes smaller than with recombinant GH [9,10]	Controlled clinical, small samples
Cognition and sleep	Healthy older adults, 5–6 months, placebo-controlled	Improved performance on several executive and fluid-intelligence measures; sleep-architecture changes inconsistent [11,12]	Randomized controlled trials
Pediatric growth hormone deficiency	Prepubertal children with idiopathic GHD	Increased height velocity over 12–36 months; response below that of somatropin; diagnostic GH provocation test [2]	Clinical trials, regulatory review
Cardiac and metabolic signaling	Rodent and porcine infarct models (GHRH agonists)	GHRH-R activation associated with reduced infarct size and cardiomyocyte apoptosis via cAMP/PKA and ERK pathways [13]	Preclinical only

GH/IGF-1 axis restoration in aging

The foundational clinical evidence comes from the Blackman group at the National Institute on Aging. Corpas and colleagues gave GHRH(1–29) to healthy men aged 60 and older for 14 days and reported that GH pulse amplitude, 24-hour integrated GH and IGF-1 rose to levels seen in men in their twenties and thirties, demonstrating that aged somatotrophs remain fully responsive [9]. Khorram, Laughlin and Yen extended the observation to 16 weeks using [Nle²⁷]GHRH(1–29)-NH₂, a closely related analog, in men and women aged 55–71; IGF-1 increased significantly and pulsatile GH secretion was preserved, with reported improvements in skin thickness and insulin sensitivity indices [10]. These studies established the key mechanistic point that distinguishes GHRH analogs from GH itself: because the pituitary and the IGF-1 feedback loop remain in the circuit, supraphysiological IGF-1 was not observed.

Body composition

Across the older-adult trials, changes in body composition were consistent in direction but small in magnitude. Khorram et al. reported increased lean body mass and reduced abdominal skinfold thickness over 16 weeks [10]. Merriam and colleagues, summarizing six-month GHRH(1–29) treatment in older men and women, described modest gains in lean mass and reductions in fat mass that did not approach those seen in earlier recombinant GH trials, and noted that muscle strength and aerobic capacity were not significantly changed [11]. The literature interprets this as the expected consequence of physiological rather than pharmacological IGF-1 levels.

Cognition and sleep

The most cited outcome in this domain is the University of Washington randomized trial reported by Vitiello and colleagues in 2006. Eighty-nine healthy adults with a mean age of 68 received GHRH(1–29) or placebo nightly for six months; the GHRH group showed statistically significant improvements on WAIS-R performance IQ, picture arrangement, verbal set-shifting and a divided-attention task, independent of sex, estrogen status or baseline ability [12]. The authors framed the result as evidence that the age-related decline of the somatotropic axis contributes to cognitive aging. The same group later reproduced the cognitive signal with tesamorelin in adults with mild cognitive impairment [12]. Sleep findings were less consistent: although GHRH acutely promotes slow-wave sleep in young adults, the six-month older-adult studies did not report robust changes in sleep architecture [11,12].

Pediatric growth hormone deficiency

Sermorelin's regulatory history rests on pediatric endocrinology. Prakash and Goa's 1999 review of the licensing data described its use as a single-dose provocative test that distinguishes pituitary from hypothalamic GH deficiency — a normal GH response after sermorelin indicates intact somatotrophs even when other stimulation tests are subnormal — and as a once-daily therapy that increased height velocity in prepubertal children with idiopathic GHD over 12 to 36 months, although the growth response was smaller than that achieved with somatropin [2]. The product was withdrawn from the US market in 2008; the withdrawal was attributed by the manufacturer to commercial factors rather than to safety findings [3].

Cardiac and metabolic signaling

A newer preclinical literature examines GHRH-R activation outside the pituitary. GHRH receptors are expressed on cardiomyocytes, and synthetic GHRH agonists have been associated in rodent and porcine myocardial-infarction models with reduced infarct size, decreased cardiomyocyte apoptosis and improved ventricular function through cAMP/PKA, ERK1/2 and Akt signaling [13]. Most of this work uses proprietary agonists (the JI and MR series) rather than sermorelin itself, so extrapolation is indirect; it is included because it defines GHRH-R pharmacology that any 1–29 agonist would be expected to share at the receptor level.

Sermorelin vs. Mod GRF 1–29, CJC-1295 and tesamorelin

Naming in this family is a persistent source of confusion in the research-supplier market. Four compounds share the GHRH(1–29) backbone and differ only in stabilizing modifications; the table summarizes the distinctions documented in the primary literature.

Compound	Structural difference from sermorelin	Reported half-life	GH release pattern	Key source
Sermorelin (GHRH 1–29)	None — native sequence	~10–20 min	Single physiological pulse	[2,6]
Mod GRF 1–29 (“CJC-1295 without DAC”)	D-Ala2, Gln8, Ala15, Leu27 (tetrasubstituted)	~30 min (estimated from analog data)	Single pulse, DPP-4 resistant	[7]
CJC-1295 with DAC	Tetrasubstituted + C-terminal Lys-maleimidopropionic acid linker that binds serum albumin Cys34	5.8–8.1 days	Sustained GH and IGF-1 elevation for 6–11 days	[7,8]
Tesamorelin (TH9507)	Full 1–44 sequence + N-terminal trans-3-hexenoyl group	~26–38 min	Pulsatile; DPP-4 resistant	[14]

Sermorelin vs. Mod GRF 1–29 (CJC-1295 no DAC)

“Modified GRF 1–29” is the tetrasubstituted GHRH(1–29) analog that Jetté and colleagues at ConjuChem built as the peptide portion of CJC-1295 [7]. When the albumin-binding Drug Affinity Complex (DAC) linker is omitted, what remains is the tetrasubstituted peptide alone — hence the supplier label “CJC-1295 without DAC.” Functionally it behaves like sermorelin: a short-acting agonist that produces one GH pulse. The four substitutions protect against DPP-4 cleavage and against the deamidation and methionine oxidation that shorten sermorelin's shelf-life in solution, so Mod GRF 1–29 is more stable both in plasma and on the bench [7]. Direct head-to-head pharmacokinetic data in humans are not published; the 30-minute half-life figure widely quoted for Mod GRF 1–29 is inferred from the preclinical characterization of the tetrasubstituted peptide rather than from a dedicated clinical study.

Sermorelin vs. CJC-1295 with DAC

The DAC version is pharmacologically a different tool. Teichman et al. reported in healthy adults that a single subcutaneous exposure raised GH two- to ten-fold for six or more days and IGF-1 1.5- to three-fold for nine to eleven days, with an estimated half-life of 5.8–8.1 days [8]. This converts the pulsatile GHRH signal into a continuous one, which is precisely what sermorelin does not do. Investigators choosing between them are therefore choosing between a probe of pulsatile physiology (sermorelin) and a tool for sustained axis activation (CJC-1295 DAC) — see the CJC-1295 research review for the full pharmacology.

Sermorelin vs. tesamorelin

Tesamorelin retains the entire 44-residue GHRH sequence and adds a hexenoyl cap at the N-terminus to block DPP-4 [14]. Its half-life is roughly twice that of sermorelin, its GH release remains pulsatile, and it carries the largest modern clinical dataset of any GHRH analog, including phase 3 studies of visceral adipose tissue and a controlled trial of hepatic fat. Sermorelin's advantages as a research reagent are its native sequence, its lower cost of synthesis and its decades-long pediatric and geriatric record; tesamorelin's are stability and regulatory-grade characterization. The tesamorelin review covers that literature in detail.

Sermorelin combined with ghrelin mimetics

Because GHRH-R and GHS-R1a signal through different second messengers (cAMP versus phospholipase C/IP₃), co-activation produces a GH response greater than the sum of either alone in both animal and human studies [5]. This synergy is why supplier catalogs frequently pair GHRH(1–29) analogs with ipamorelin or GHRP-6. The mechanistic basis is well documented; the combinations themselves have not been studied in controlled trials with sermorelin specifically.

Limitations and research considerations

• Small, aged cohorts. The principal clinical studies enrolled between 10 and 89 participants, nearly all over age 55, and none exceeded twelve months. Effects on hard outcomes were not assessed [9,10,11,12].
• Analog heterogeneity. Several landmark “sermorelin” findings used [Nle²⁷]GHRH(1–29) or unspecified GHRH(1–29) preparations; results are frequently pooled across analogs in secondary literature without noting the differences [10,11].
• Stability in solution. Native Asn⁸ deamidation and Met²⁷ oxidation degrade sermorelin in aqueous solution; analytical confirmation of purity and identity after reconstitution is a prerequisite for interpretable in-vitro work [7].
• Naming ambiguity in supplier markets. Products labelled “CJC-1295” may be either the DAC or non-DAC peptide, which differ in half-life by two orders of magnitude; certificates of analysis specifying sequence and mass are the only reliable disambiguation [7,8].
• IGF-1 feedback assumptions. The claim that GHRH analogs cannot produce supraphysiological IGF-1 rests on intact pituitary feedback; it does not hold in cell-culture systems or in models with disrupted somatostatin tone [4].
• Extra-pituitary receptor data are indirect. Cardiac and metabolic GHRH-R findings derive from proprietary agonists, not sermorelin, and remain preclinical [13].

Where to source for research

Sermorelin acetate intended for laboratory investigation should be obtained only from suppliers that publish third-party analytical documentation — ideally HPLC purity and mass-spectrometry identity for each lot — and that label material unambiguously as research-use-only. Given the naming overlap with Mod GRF 1–29 and CJC-1295, the certificate of analysis should state the exact sequence and molecular mass. Short Chain Aminos publishes batch-level analytical documentation for its research catalog, and comparable GHRH-analog material is listed by BioPep, Catalyst Research, and Apex Research Services. Our guide to evaluating research peptide suppliers outlines the documentation to request and the red flags to avoid. This information is provided as a research-availability reference only and is not a purchasing recommendation.

Frequently asked research questions

What is sermorelin?

Sermorelin is a synthetic peptide consisting of the first 29 amino acids of human growth hormone–releasing hormone. It is the shortest GHRH fragment with full biological activity, acts on the pituitary GHRH receptor to trigger pulsatile growth-hormone release, and was formerly licensed under the brand name Geref for pediatric diagnostic and therapeutic use.

Is sermorelin a peptide or a hormone?

Both descriptions are accurate. Sermorelin is a 29-residue peptide, and because it is a fragment of a hypothalamic hormone acting on a pituitary receptor it is classed pharmacologically as a peptide hormone analog. It is not growth hormone itself; it is an upstream secretagogue that causes the pituitary to release stored GH.

What is the difference between sermorelin and CJC-1295 without DAC?

CJC-1295 without DAC, also called Mod GRF 1–29, has the same 29-residue backbone as sermorelin with four amino-acid substitutions (D-Ala², Gln⁸, Ala¹⁵, Leu²⁷) that resist enzymatic breakdown and oxidation. Both produce a single GH pulse; the modified peptide is more stable in plasma and in solution.

How does sermorelin differ from CJC-1295 with DAC?

CJC-1295 with DAC carries a linker that binds serum albumin, extending its half-life to roughly six to eight days and producing continuous GH and IGF-1 elevation. Sermorelin has a half-life of minutes and produces one physiological pulse. They are studied as tools for different questions: pulsatile versus sustained axis activation.

How does sermorelin compare with tesamorelin?

Tesamorelin is the full 44-residue GHRH sequence with an N-terminal hexenoyl group that blocks DPP-4 degradation, giving it roughly twice sermorelin's half-life and a larger modern clinical dataset. Sermorelin is the unmodified 1–29 fragment with a longer historical record in pediatric and geriatric endocrinology research.

Why is sermorelin's half-life so short?

The enzyme dipeptidyl peptidase-4 cleaves the bond between alanine-2 and aspartate-3 within minutes of the peptide entering plasma, producing an inactive fragment. A secondary trypsin-like cleavage occurs at residues 11–12. This was characterized by Frohman and colleagues in 1989 and motivated every subsequent stabilized analog.

Is sermorelin still approved?

Sermorelin acetate was approved in the United States in 1997 as Geref for diagnosing and treating pediatric growth-hormone deficiency. The manufacturer withdrew the product in 2008, citing commercial rather than safety reasons. It is currently available only as a research reagent.

What did the cognition studies with GHRH(1–29) report?

A six-month randomized placebo-controlled trial in 89 healthy older adults reported significant improvements on several fluid-intelligence and executive measures, independent of sex or baseline ability. The authors interpreted the result as evidence linking somatotropic-axis decline to cognitive aging; the finding was later reproduced with tesamorelin in mild cognitive impairment.

Works Cited

1. 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.” Proceedings of the National Academy of Sciences USA. 1984;81(14):4302–4306. PMID: 6431406. DOI: 10.1073/pnas.81.14.4302.
2. Prakash A, Goa KL. “Sermorelin: a review of its use in the diagnosis and treatment of children with idiopathic growth hormone deficiency.” BioDrugs. 1999;12(2):139–157. PMID: 18031173. DOI: 10.2165/00063030-199912020-00007.
3. Walker RF. “Sermorelin: a better approach to management of adult-onset growth hormone insufficiency?” Clinical Interventions in Aging. 2006;1(4):307–308. PMID: 18046908. PMCID: PMC2699646.
4. Mayo KE. “Molecular cloning and expression of a pituitary-specific receptor for growth hormone-releasing hormone.” Molecular Endocrinology. 1992;6(10):1734–1744.
5. Ishida J, Saitoh M, Ebner N, Springer J, Anker SD, von Haehling S. “Growth hormone secretagogues: history, mechanism of action, and clinical development.” JCSM Rapid Communications. 2020;3(1):25–37. DOI: 10.1002/rco2.9.
6. Frohman LA, Downs TR, Heimer EP, Felix AM. “Dipeptidylpeptidase IV and trypsin-like enzymatic degradation of human growth hormone-releasing hormone in plasma.” Journal of Clinical Investigation. 1989;83(5):1533–1540. DOI: 10.1172/JCI114049.
7. Jetté L, Léger R, Thibaudeau K, et al. “Human growth hormone-releasing factor (hGRF)1-29-albumin bioconjugates activate the GRF receptor on the anterior pituitary in rats: identification of CJC-1295 as a long-lasting GRF analog.” Endocrinology. 2005;146(7):3052–3058. PMID: 15817669. DOI: 10.1210/en.2004-1286.
8. Teichman SL, Neale A, Lawrence B, Gagnon C, Castaigne JP, Frohman LA. “Prolonged stimulation of growth hormone (GH) and insulin-like growth factor I secretion by CJC-1295, a long-acting analog of GH-releasing hormone, in healthy adults.” Journal of Clinical Endocrinology & Metabolism. 2006;91(3):799–805. PMID: 16352683. DOI: 10.1210/jc.2005-1536.
9. Corpas E, Harman SM, Piñeyro MA, Roberson R, Blackman MR. “Growth hormone (GH)-releasing hormone-(1-29) twice daily reverses the decreased GH and insulin-like growth factor-I levels in old men.” Journal of Clinical Endocrinology & Metabolism. 1992;75(2):530–535. PMID: 1379256. DOI: 10.1210/jcem.75.2.1379256.
10. Khorram O, Laughlin GA, Yen SS. “Endocrine and metabolic effects of long-term administration of [Nle27]growth hormone-releasing hormone-(1-29)-NH2 in age-advanced men and women.” Journal of Clinical Endocrinology & Metabolism. 1997;82(5):1472–1479. PMID: 9141536. DOI: 10.1210/jcem.82.5.3943.
11. Merriam GR, Schwartz RS, Vitiello MV. “Growth hormone-releasing hormone and growth hormone secretagogues in normal aging.” Endocrine. 2003;22(1):41–48. DOI: 10.1385/ENDO:22:1:41.
12. Vitiello MV, Moe KE, Merriam GR, Mazzoni G, Buchner DH, Schwartz RS. “Growth hormone releasing hormone improves the cognition of healthy older adults.” Neurobiology of Aging. 2006;27(2):318–323. PMID: 16399214. DOI: 10.1016/j.neurobiolaging.2005.01.010. See also Baker LD, et al. Archives of Neurology. 2012;69(11):1420–1429 (tesamorelin in MCI).
13. Kanashiro-Takeuchi RM, Szalontay L, Schally AV, et al. “New therapeutic approach to heart failure due to myocardial infarction based on targeting growth hormone-releasing hormone receptor.” Oncotarget. 2015;6(12):9728–9739. DOI: 10.18632/oncotarget.3303.
14. Falutz J, Allas S, Blot K, et al. “Metabolic effects of a growth hormone–releasing factor in patients with HIV.” New England Journal of Medicine. 2007;357(23):2359–2370. PMID: 18057338. DOI: 10.1056/NEJMoa072375.

Research Use Only. The information above summarizes published preclinical and clinical literature for laboratory reference. It is not medical advice and does not describe or endorse any human or veterinary use, dosing, or administration. Sermorelin and the related GHRH analogs discussed here are intended solely for in-vitro and research applications.

Explore related compounds: Tesamorelin · CJC-1295 · Ipamorelin · GHRP-6 · IGF-1 LR3