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Peptide Science Journal
Structural & Mechanism

Sermorelin and the GHRH Analog Class: A Research Overview

Sermorelin is a synthetic 29-amino-acid peptide that corresponds to the first 29 residues of growth hormone-releasing hormone (GHRH), the endogenous hypothalamic peptide that stimulates somatotroph release of growth hormone (GH) from the anterior pituitary. The GHRH(1-29) fragment was identified in the early 1980s as the minimal sequence retaining full receptor-binding activity, and it became the prototype for a broader class of synthetic GHRH analogs that are now studied in research applications spanning growth-hormone-axis biology, aging-research biomarkers, and somatotroph pharmacology.

This article is a research-context overview of sermorelin and the GHRH analog class. It covers the receptor biology, the structural design considerations that motivated the various analogs, and the published animal-research literature. In line with the research-use-only framing of all research-peptide content, the framing is research-use only — these compounds are sold for laboratory and animal-research applications, not for any clinical or human-use purpose.

GHRH biology in brief

Growth hormone-releasing hormone is a 44-amino-acid peptide produced in the arcuate and ventromedial nuclei of the hypothalamus. GHRH is released into the hypothalamic-hypophyseal portal blood and travels to the anterior pituitary, where it binds the GHRH receptor (GHRHR) on somatotroph cells. GHRHR is a Gs-protein-coupled receptor; receptor activation increases intracellular cyclic AMP via adenylyl cyclase, which in turn stimulates GH transcription and the pulsatile release of stored GH.

The minimal active fragment of GHRH is the N-terminal 29 amino acids — GHRH(1-29) — which retains full intrinsic receptor-binding activity. The C-terminal residues (30-44) are dispensable for receptor activation but contribute to the pharmacokinetic stability of the parent molecule. This structure-function relationship was established by Frohman and colleagues in foundational work reviewed in Frohman LA, Jansson JO, “Growth hormone-releasing hormone,” Endocrine Reviews 7(3):223–253, 1986 (DOI: 10.1210/edrv-7-3-223).

The GHRH(1-29) fragment, in the unmodified synthetic form, is sermorelin.

Sermorelin: structure and identity

Sermorelin is the synthetic 29-amino-acid peptide H-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. Its molecular weight is approximately 3358 Da and its empirical formula is C₁₄₉H₂₄₆N₄₄O₄₂S. The CAS registry number is 86168-78-7. As a research peptide, sermorelin is supplied as a lyophilized powder.

The C-terminal amide on the natural GHRH peptide is retained in sermorelin. The peptide is intrinsically susceptible to proteolytic degradation in plasma — primarily by dipeptidyl peptidase-4 (DPP-4) cleavage at the Tyr-Ala bond at the N-terminus — which limits its circulating half-life to a few minutes. This pharmacokinetic limitation motivated the development of stabilized analogs (see below).

The CJC-1295, tesamorelin, and GHRH-analog family

The GHRH(1-29) backbone has been the starting point for several stabilized research analogs. The key structural strategies are:

  1. N-terminal modification (e.g., D-Ala²) to block DPP-4 cleavage. This is the basis for the modified-GRF (Mod-GRF 1-29) analog, also marketed as CJC-1295 without DAC.
  2. Drug Affinity Complex (DAC) technology — attachment of a reactive maleimidopropionic acid linker that covalently binds plasma albumin. The albumin conjugate has a circulating half-life of approximately one week. This is the basis for CJC-1295 with DAC.
  3. Hexenoyl modification — addition of a trans-3-hexenoyl fatty acid to the N-terminal tyrosine. This is the basis for tesamorelin, the most extensively clinically-studied GHRH analog.

Each of these strategies is a pharmacokinetic modification — extending the time the analog spends in circulation, and therefore the duration of receptor stimulation — without changing the underlying GHRHR-binding mechanism. The pharmacodynamic profile of the analog (the receptor-binding affinity, the intracellular signaling cascade, the negative-feedback regulation by somatostatin and IGF-1) remains substantially similar to the parent GHRH peptide.

The GHRH-receptor mechanism — what is established and what is reported

The mechanism by which sermorelin and the broader GHRH-analog class influences the somatotroph axis is well-characterized at the molecular level:

  • Receptor binding — sermorelin binds the GHRHR with affinity comparable to the parent GHRH peptide. The structural basis of this interaction was characterized in the analog series developed by Felix, Heimer, Mowles, and colleagues in the late 1980s.
  • Intracellular signaling — receptor activation couples to Gs, increases cyclic AMP via adenylyl cyclase, and activates the cAMP-responsive element binding (CREB) transcription factor, which drives GH transcription.
  • Pulsatile release — somatotroph response to GHRH stimulation is intrinsically pulsatile and is modulated by reciprocal somatostatin tone from the periventricular nucleus of the hypothalamus. The result of a single GHRH-analog stimulation is a transient GH pulse rather than a sustained elevation.
  • Negative feedback — released GH stimulates hepatic IGF-1 production. IGF-1 (and GH itself, via short-loop feedback) suppresses somatotroph responsiveness to subsequent GHRH stimulation. This is the physiologic feedback loop that distinguishes upstream secretagogue stimulation (sermorelin, CJC-1295, tesamorelin) from exogenous GH administration.

Foundational characterization is reviewed in Frohman LA, Jansson JO, Endocrine Reviews 1986 (cited above), and in subsequent work on the GHRH-receptor crystal structure by various groups.

Published animal-research and clinical-research findings

The published GHRH-analog research literature spans both animal-model investigation and clinical-research studies. Representative areas of investigation include:

  • GH pulsatility and somatotroph reserve — animal studies have used sermorelin and other GHRH analogs as research probes for the integrity of the GH axis. This is the diagnostic-research application that motivated the original development of these compounds.
  • Aging-research biomarkers — sermorelin has been used in research on the age-related decline in GH secretion, with published work investigating the dynamic GH-response to GHRH stimulation as a function of age in animal models.
  • Tesamorelin clinical research — tesamorelin has a substantial clinical-research literature, including the Phase 3 program reported in Falutz J, et al., “Effects of tesamorelin (TH9507), a growth hormone-releasing factor analog, in human immunodeficiency virus-infected patients with excess abdominal fat: a pooled analysis of two multicenter, double-blind placebo-controlled phase 3 trials with safety extension data,” Journal of Clinical Endocrinology & Metabolism 95(9):4291–4304, 2010 (DOI: 10.1210/jc.2010-0490). This clinical literature is included for completeness of the GHRH-analog research record; the product in this catalog is sold for research use only.

The unmodified sermorelin compound was historically the subject of preclinical and clinical research as a probe of GH-axis function. Most published work in this area is from the 1990s and early 2000s.

Reading a sermorelin or GHRH-analog CoA

A research-grade CoA for sermorelin or any GHRH analog should document the molecular weight (≈3358 Da for sermorelin; the analog-specific MW for CJC-1295, tesamorelin, etc.), HPLC purity ≥99.0%, mass spectrometry confirmation, and net peptide content. The amino acid sequence on the CoA should match the published reference sequence for the compound. For tesamorelin, the CoA should also document the trans-3-hexenoyl modification on the N-terminus.

For a step-by-step guide on reading a peptide CoA, see article on how to read a peptide Certificate of Analysis.

Storage notes

Sermorelin and the GHRH-analog class are supplied as lyophilized powders. Storage protocols:

  • Lyophilized vial: -20°C, dry, protected from light. Stable for extended periods (typically 1-2+ years) when properly sealed.
  • Reconstituted: 2-8°C in sterile bacteriostatic water. Reconstituted sermorelin has a typical refrigerated stability of 2-3 weeks.
  • For long-term storage of reconstituted material: aliquot into single-use volumes, freeze at -20°C, thaw each aliquot once.

The DAC-conjugated analog (CJC-1295 with DAC) has somewhat different stability behavior owing to the maleimide-albumin linker; vendor-specific storage guidance on the CoA should be consulted.

Summary

Sermorelin is the synthetic 29-amino-acid peptide corresponding to the active fragment of growth hormone-releasing hormone. It is the prototype of a class of research peptides — including CJC-1295 (with and without DAC) and tesamorelin — that share the GHRH-receptor binding mechanism and differ primarily in their pharmacokinetic stability profiles. The receptor biology is well-characterized; the published research literature spans animal-model GH-axis investigation and (for tesamorelin specifically) extensive clinical-research data. As research-use compounds, sermorelin and the GHRH analogs are intended for laboratory and animal-research investigation of the somatotroph axis.

Selected sources

  1. Frohman LA, Jansson JO. “Growth hormone-releasing hormone.” Endocrine Reviews 7(3):223–253, 1986. DOI: 10.1210/edrv-7-3-223.
  2. Felix AM, Heimer EP, Mowles TF, et al. “Synthesis, biological activity and conformational analysis of cyclic GRF analogs.” International Journal of Peptide and Protein Research 32(6):441–454, 1988.
  3. Falutz J, Mamputu JC, Potvin D, Moyle G, Soulban G, Loughrey H, Marsolais C, Turner R, Grinspoon S. “Effects of tesamorelin (TH9507), a growth hormone-releasing factor analog, in human immunodeficiency virus-infected patients with excess abdominal fat: a pooled analysis of two multicenter, double-blind placebo-controlled phase 3 trials with safety extension data.” Journal of Clinical Endocrinology & Metabolism 95(9):4291–4304, 2010. DOI: 10.1210/jc.2010-0490.
  4. Walker RF. “Sermorelin: a better approach to management of adult-onset growth hormone insufficiency?” Clinical Interventions in Aging 1(4):307–308, 2006. DOI: 10.2147/ciia.2006.1.4.307.
  5. Mayo KE, Godfrey PA, Suhr ST, Kulik DJ, Rahal JO. “Growth hormone-releasing hormone: synthesis and signaling.” Recent Progress in Hormone Research 50:35–73, 1995.

Research Use Only — Disclaimer

The research peptides discussed on this page are described for laboratory and research purposes only. They are intended exclusively for in vitro experimentation and for use in animal studies under appropriate institutional oversight. They are not drugs, dietary supplements, cosmetics, or food additives. They are not for human consumption, not for veterinary use in companion animals, and not for any therapeutic, diagnostic, preventive, or palliative purpose.

Nothing on this page constitutes medical advice. The clinical-research literature referenced for tesamorelin is included as part of the GHRH-analog research record and does not constitute a recommendation, claim, or representation that any of these compounds is safe, effective, or appropriate for any human use.

Buyers must be at least 21 years of age and must agree to use products strictly for research purposes.