Tesamorelin
A stabilised analogue of growth hormone-releasing factor (GRF 1-44), and the growth hormone axis peptide with the largest body of randomised clinical literature behind it. This guide covers what it is, how it acts on the pituitary, and what the published research actually measured.
Overview
Tesamorelin is a synthetic analogue of human growth hormone-releasing hormone (GHRH), the 44-amino-acid hypothalamic factor also written as GRF 1-44. Native GHRH is the upstream signal that instructs the anterior pituitary to release growth hormone (GH). It is also extremely short-lived in circulation, because the enzyme dipeptidyl peptidase-4 (DPP-4) cleaves it rapidly at the N-terminus. Tesamorelin was designed to solve that problem: a trans-3-hexenoyl group is attached to the N-terminal tyrosine, which sterically hinders DPP-4 cleavage and gives the molecule a materially longer functional window than unmodified GRF 1-44 while leaving the receptor-binding region intact.
What separates Tesamorelin from most compounds in the research peptide category is the depth of its published record. It is the GH-axis peptide that has been through large multicentre, double-blind, placebo-controlled phase 3 trials, with visceral adipose tissue (VAT) measured by CT as a pre-specified primary endpoint, and with later work extending into hepatic fat content. For a researcher designing a GH-axis study, this means the mechanism is not inferred from cell work or analogy: there is human endpoint data describing what happens when the GHRH receptor is stimulated in a sustained, controlled way.
Tesamorelin is frequently studied and discussed alongside the secretagogue class, which reaches the same downstream output through an entirely different receptor. That distinction is set out in the Tesamorelin vs Ipamorelin comparison.
Molecular Profile
| Class | Growth hormone-releasing factor (GHRH/GRF) analogue |
| Amino acid length | 44 residues (GRF 1-44 sequence) |
| Structural modification | trans-3-hexenoyl moiety on the N-terminal tyrosine, conferring resistance to DPP-4 cleavage |
| Molecular formula | C221H366N72O67S |
| Molecular weight | Approximately 5135.9 g/mol |
| CAS number | 218949-48-5 (free base); 901758-09-6 (acetate) |
| Reported half-life | Short, on the order of tens of minutes in published pharmacokinetic work, with the biological effect outlasting plasma presence because the signal acts upstream on pituitary release |
| Presentation | Lyophilised powder, reconstituted for laboratory use |
Mechanism of Action
Tesamorelin binds the GHRH receptor (GHRH-R), a G protein-coupled receptor expressed on the somatotroph cells of the anterior pituitary. Receptor occupancy activates the Gs/adenylate cyclase pathway, raising intracellular cAMP and triggering release of stored growth hormone. Released GH then acts on peripheral tissue, principally the liver, where it drives production of insulin-like growth factor 1 (IGF-1), the main circulating mediator of GH activity.
The mechanistically important point is that Tesamorelin is a secretagogue of the endogenous system, not exogenous growth hormone. It amplifies the body's own pulsatile release pattern rather than replacing it with a flat, externally supplied concentration. Because the pituitary remains subject to negative feedback from somatostatin and from circulating IGF-1, the physiological ceiling on release is preserved. This is the principal reason GHRH-analogue approaches are studied separately from direct recombinant GH administration, and why the two produce different research profiles despite converging on the same axis.
The DPP-4 resistance conferred by the hexenoyl modification is what makes the molecule practical to study. Native GRF 1-44 is degraded so quickly that maintaining a meaningful stimulus is difficult; stabilising the N-terminus extends the window over which the receptor signal is delivered.
Key Published Research
Metabolic effects of a growth hormone-releasing factor in patients with HIV
Falutz J, et al. New England Journal of Medicine. 2007; 357(23):2359-2370 (PMID 18057338)
The pivotal randomised, double-blind, placebo-controlled trial in patients with HIV-associated abdominal fat accumulation. Visceral adipose tissue measured by CT was the primary endpoint, and the trial also reported changes in triglycerides and the total-to-HDL cholesterol ratio. This is the study that established Tesamorelin as the GH-axis peptide most cited in fat-distribution research.
Effects of tesamorelin (TH9507) in HIV-infected patients with excess abdominal fat: a pooled analysis of two phase 3 trials with safety extension data
Falutz J, et al. Journal of Acquired Immune Deficiency Syndromes. 2010 (PMID 20554713)
Pooled analysis across both multicentre phase 3 trials, with extension data. Relevant because it examines the durability of the observed effect and what happens on withdrawal, which is the question single-trial data cannot answer.
Effect of tesamorelin on visceral fat and liver fat in HIV-infected patients with abdominal fat accumulation: a randomized clinical trial
Stanley TL, et al. JAMA. 2014; 312(4):380-389 (PMID 25038357)
Extends the endpoint set from visceral adipose tissue to hepatic fat content, the study most often cited when the research question concerns liver fat rather than fat distribution alone.
Storage and Handling
Lyophilised (unreconstituted):Store at -20°C for long-term stability. Keep sealed and protected from light and moisture.
Reconstituted:Store at 2-8°C and use within roughly 30 days. Avoid repeated freeze-thaw cycles.
Recommended solvent: Bacteriostatic water or sterile water for laboratory use. See the reconstitution reference for concentration calculations.
Frequently Asked Questions
What is Tesamorelin?
A synthetic 44-amino-acid analogue of growth hormone-releasing hormone (GRF 1-44), modified with a trans-3-hexenoyl group on the N-terminal tyrosine so that it resists enzymatic degradation by DPP-4. It acts on the GHRH receptor of the anterior pituitary.
How does Tesamorelin differ from growth hormone itself?
Growth hormone is the downstream hormone. Tesamorelin is an upstream signal that prompts the pituitary to release its own stored growth hormone, so the endogenous pulsatile pattern and its negative feedback controls remain in place rather than being bypassed.
Why is Tesamorelin associated with visceral fat in the literature?
Because its pivotal randomised trials used change in visceral adipose tissue, measured by CT, as the primary endpoint (Falutz et al., 2007), with later work adding hepatic fat (Stanley et al., 2014). The association reflects what the trials were designed to measure.
How does it compare to Ipamorelin or Sermorelin?
Sermorelin is a shorter GHRH fragment (GRF 1-29) acting on the same receptor without the stabilising modification. Ipamorelin is not a GHRH analogue at all: it acts on the separate ghrelin/GH secretagogue receptor. See the Tesamorelin vs Ipamorelin and Ipamorelin vs Sermorelin comparisons.
What purity should it be for research?
≥98% purity as verified by HPLC, with a certificate of analysis available to confirm purity and identity.
Researchers working across the growth hormone axis may also reference the Ipamorelin research guide and the Tesamorelin vs Ipamorelin comparison.
Disclaimer: This information is compiled from published peer-reviewed literature and is provided for educational and research reference purposes only. It does not constitute medical advice. The peptides referenced here, sold by Enhanced Research Compounds, are intended exclusively for in-vitro research and laboratory use. They are not therapeutic goods, are not listed on the ARTG, and are not approved for human or animal consumption.