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title: Tesamorelin (GHRH Analog): A Synthetic GRF 1–44 Analogue description: "Tesamorelin is a synthetic 44-amino-acid analog of human growth hormone-releasing hormone (GHRH), also referred to as GR"

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Tesamorelin (GHRH Analog): A Synthetic GRF 1–44 Analogue

Quick Facts

Full Name	Tesamorelin (INN); TH9507 (developmental code)
Class	Synthetic growth hormone-releasing hormone (GHRH) analog / GRF 1–44 analogue
Molecular Formula	C₂₂₁H₃₆₆N₇₂O₆₇S
Molecular Weight	~5,135 Da
Amino Acid Length	44 amino acids
Mechanism	GHRH receptor agonist; stimulates pituitary GH secretion
Sequence Homology	Identical to endogenous human GHRH (1–44) with a single substitution: norleucine for methionine at position 27
Route of Administration	Subcutaneous injection
Regulatory Status	FDA-approved (Egrifta) for HIV-associated lipodystrophy (2010)
PubChem CID	16135177
CAS Number	948594-65-8

Executive Summary

Tesamorelin is a synthetic 44-amino-acid analog of human growth hormone-releasing hormone (GHRH), also referred to as GRF (growth hormone-releasing factor) 1–44.

It differs from endogenous GHRH by a single substitution-norleucine (Nle) in place of methionine (Met) at position 27-which confers enhanced metabolic stability against dipeptidyl peptidase-4 (DPP-IV) degradation.

Tesamorelin acts as a selective GHRH receptor agonist, stimulating the pulsatile release of endogenous growth hormone (GH) from the anterior pituitary. It received FDA approval in 2010 under the brand name Egrifta for the reduction of excess visceral abdominal fat in HIV-infected patients with lipodystrophy.

Ongoing research investigates its potential applications in metabolic disorders, sarcopenia, and hepatic steatosis.

Introduction

Growth hormone-releasing hormone (GHRH) is a hypothalamic peptide that plays a central role in the somatotropic axis by stimulating the synthesis and pulsatile secretion of growth hormone.

In 1982, Rivier and colleagues first isolated and characterized human GHRH from pancreatic tumors that caused acromegaly, identifying both the 44-amino-acid (GHRH 1–44) and 37-amino-acid (GHRH 1–37) isoforms. The 1–44 isoform is the predominant circulating form and possesses full biological activity.

Tesamorelin was developed as a synthetic equivalent to endogenous GHRH (1–44) with a single amino acid substitution designed to resist enzymatic cleavage.

This modification extends the peptide's circulating half-life without altering its receptor-binding profile, making it a pharmacologically valuable tool for studying the somatotropic axis in both preclinical and clinical settings.

Molecular Characteristics

The primary structure of tesamorelin is 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-Nle-Ser-Arg-Gln-Gln-Gly-Glu-Ser-Asn-Gln-Glu-Arg-Gly-Ala-Arg-Ala-Arg-Leu-NH₂.

The C-terminal leucinamide replaces the natural free acid, and the Met→Nle substitution at position 27 prevents oxidation and DPP-IV-mediated cleavage. The peptide is typically supplied as a lyophilized powder formulated with mannitol, sodium phosphate, and sodium hydroxide for pH adjustment upon reconstitution.

Its molecular mass of approximately 5,135 Da places it in the category of medium-length therapeutic peptides. Tesamorelin is hydrophilic and requires subcutaneous administration; oral bioavailability is negligible due to gastrointestinal proteolysis, consistent with most peptide therapeutics.

Biological Research Background

GHRH Receptor Signaling

Tesamorelin binds selectively to the GHRH receptor (GHRHR), a G-protein-coupled receptor (GPCR) expressed predominantly on somatotroph cells of the anterior pituitary. Upon ligand binding, GHRHR activates the adenylate cyclase–cAMP–PKA signaling cascade, promoting GH gene transcription and exocytosis of stored GH secretory granules. Endogenous GH, in turn, stimulates hepatic insulin-like growth factor 1 (IGF-1) production, which mediates many of the peripheral anabolic effects of the somatotropic axis.

Impact on Body Composition and Metabolism

In HIV-infected patients with antiretroviral therapy-associated lipodystrophy, tesamorelin consistently reduces visceral adipose tissue (VAT) accumulation-a key driver of cardiometabolic risk. Randomized controlled trials demonstrate reductions in VAT of 15–20% over 26 weeks compared with placebo, with sustained effects over 52 weeks of continued treatment. Importantly, the peptide does not impair glycemic control; some studies report modest improvements in insulin sensitivity, likely attributable to the GH-induced lipolytic profile rather than direct insulinotropic effects.

Hepatic Effects

Recent evidence suggests that tesamorelin may reduce hepatic fat content in patients with HIV-associated non-alcoholic fatty liver disease (NAFLD). In a randomized, placebo-controlled trial by Stanley and colleagues, tesamorelin treatment over 12 months led to a significant reduction in liver fat measured by magnetic resonance spectroscopy, along with improvements in hepatic biomarkers. These findings support further investigation of GHRH analogs in metabolic liver disease.

Current Research Landscape

Contemporary research on tesamorelin extends beyond HIV-associated lipodystrophy into several adjacent domains:

• Non-alcoholic steatohepatitis (NASH): Given its ability to reduce hepatic steatosis, tesamorelin is being explored as a potential therapy for NASH, a condition with limited pharmacological options.
• Sarcopenia and frailty: By boosting endogenous GH and IGF-1 levels, tesamorelin may have applications in age-related muscle wasting, though long-term safety data in elderly populations remain limited.
• Cognitive function: GHRH and its analogs have demonstrated neuroprotective and cognitive-enhancing properties in both animal models and early human studies, likely mediated through IGF-1-dependent and independent pathways.
• Cardiovascular risk: Studies are evaluating whether the beneficial effects of tesamorelin on VAT, lipids, and inflammatory biomarkers translate into reduced cardiovascular event rates.

Related Research

Ipamorelin Research Profile

Ghrelin mimetic for comparative endocrine research.

Metabolic Research

Metabolic hormone research applications.

GLP-1 Peptide Research Overview

Metabolic peptide hormone research context.

Frequently Asked Questions

+ **What distinguishes tesamorelin from endogenous GHRH?**

Tesamorelin differs from endogenous human GHRH (1–44) by a single amino acid substitution: norleucine replaces methionine at position 27. This modification increases resistance to dipeptidyl peptidase-4 (DPP-IV) enzymatic degradation, extending the peptide's circulating half-life while maintaining full receptor-binding affinity.

+ **Is tesamorelin a growth hormone secretagogue?**

Yes, tesamorelin acts as a growth hormone secretagogue through stimulation of the GHRH receptor. However, unlike ghrelin mimetics (e.g., ipamorelin) that act on the GHS-R1a receptor, tesamorelin directly mimics the action of endogenous GHRH by binding to the GHRHR on pituitary somatotroph cells.

+ **What is the regulatory status of tesamorelin?**

Tesamorelin (Egrifta) is FDA-approved for the reduction of excess visceral abdominal fat in HIV-infected patients with lipodystrophy. It has also received marketing authorization in Canada. It remains an investigational compound for other indications.

+ **Does tesamorelin affect blood glucose levels?**

Clinical studies indicate that tesamorelin does not adversely affect glycemic control. Some evidence points to modest improvements in insulin sensitivity, likely due to GH-induced lipolysis and reduction of visceral adiposity. However, GH can induce transient insulin resistance, and glucose monitoring remains standard in clinical trials.

+ **What are the most common adverse events associated with tesamorelin?**

The most frequently reported adverse events in clinical trials include injection-site reactions (erythema, pruritus), arthralgias, myalgias, and peripheral edema. These are generally mild to moderate and are consistent with the known effects of GH axis stimulation.

+ **Can tesamorelin be administered orally?**

No. Like most peptides of its size, tesamorelin undergoes rapid proteolytic degradation in the gastrointestinal tract and has negligible oral bioavailability. It is formulated exclusively for subcutaneous injection.

+ **How does tesamorelin compare with systemic GH therapy?**

Tesamorelin preserves the endogenous pulsatile pattern of GH secretion by stimulating the pituitary's natural feedback mechanisms, whereas exogenous GH administration delivers supraphysiological, non-pulsatile GH levels. The pulsatile profile achieved with tesamorelin may offer a more physiologic approach with a potentially more favorable safety profile.

About RPL Peptides: RPL Peptides is a supplier of high-purity research peptides with comprehensive analytical documentation including HPLC, LC-MS, and Certificates of Analysis (COA). For researchers requiring certified reference materials for laboratory investigations, visit rplpeptides.com or explore detailed molecular data at the RPL Peptides Data Center.

References

- Falutz J, Allas S, Blot K, et al. Metabolic effects of a growth hormone-releasing factor in patients with HIV. N Engl J Med. 2007;357(23):2359-2370. doi:10.1056/NEJMoa072664 - Stanley TL, Feldpausch MN, Oh J, et al. Effect of tesamorelin on visceral fat and liver fat in HIV-infected patients with abdominal fat accumulation: a randomized clinical trial. AIDS. 2014;28(9):1299-1307. doi:10.1097/QAD.0000000000000256 - Falutz J, Potvin D, Mamputu JC, et al. Long-term safety and effects of tesamorelin in HIV patients with abdominal fat accumulation. AIDS. 2008;22(13):1665-1676. doi:10.1097/QAD.0b013e3283030d91 - Grunfeld C, Dobs AS, Engelson E, et al. Effects of tesamorelin on visceral adiposity in HIV-infected patients with abdominal fat accumulation. J Clin Endocrinol Metab. 2009;94(11):4286-4294. doi:10.1210/jc.2009-1330 - Koutkia P, Canavan B, Breu J, et al. Growth hormone-releasing hormone (GHRH) administration in HIV-infected men: effects on body composition. J Clin Endocrinol Metab. 2005;90(5):2795-2800. doi:10.1210/jc.2004-2099 - Dhillon S. Tesamorelin: a review of its use in the management of HIV-associated lipodystrophy. Drugs. 2011;71(8):1071-1091. doi:10.2165/11207480-000000000-00000 - Suh HS, Zhao Y, Smith N, et al. Tesamorelin for HIV-associated lipodystrophy: a systematic review. Clin Ther. 2014;36(10):1509-1522. doi:10.1016/j.clinthera.2014.08.004 - Lo J, You SM, Liebau J, et al. Effects of tesamorelin on coronary vascular function in HIV-infected patients. HIV Med. 2016;17(8):580-588. doi:10.1111/hiv.12381