Mechanism
Tesamorelin is a synthetic analog of human growth hormone-releasing hormone (GHRH), specifically GRF(1-44) with a trans-3-hexenoic acid added to the N-terminus. The modification stabilizes the molecule against enzymatic degradation, extending the half-life from native GHRH’s minutes to approximately 26 minutes — long enough for once-daily subcutaneous dosing.
The mechanism is GHRH-receptor agonism on anterior pituitary somatotrophs, stimulating endogenous GH secretion in a relatively physiologic pulsatile pattern. The downstream effect is elevated GH and IGF-1, which in HIV-associated lipodystrophy patients produces preferential mobilization of visceral adipose tissue.
The HIV-lipodystrophy connection is mechanistically interesting: antiretroviral therapy (particularly older protease inhibitors) causes a characteristic redistribution of body fat — reduced subcutaneous fat, increased visceral fat — that is metabolically harmful and visibly distressing to patients. The GHRH-stimulated GH increase preferentially reduces visceral fat without significantly affecting subcutaneous fat, addressing the specific lipodystrophy phenotype.
What the evidence shows
Phase 3 trials in HIV-associated lipodystrophy:
- Falutz et al, NEJM 2007: 412 patients, 26-week trial of tesamorelin 2 mg daily versus placebo. Visceral adipose tissue (VAT) reduced by 15.2% in treatment group versus +5.0% in placebo.
- Falutz et al, AIDS 2008: Long-term extension showing sustained VAT reduction at 52 weeks.
- Stanley et al, J Clin Endocrinol Metab 2012: Confirmation in independent cohort.
These are real RCTs in the indication-relevant population, with imaging-based endpoints (VAT measured by CT/MRI) and clinically meaningful effect sizes.
For off-label body-composition use:
No comparable RCT evidence in metabolically healthy adults. The mechanism that produces visceral fat reduction in HIV-lipodystrophy (preferential mobilization in a specifically dysregulated fat-distribution phenotype) may not generalize. Some studies in non-HIV obesity have shown modest VAT reduction; the effect sizes are smaller and the clinical relevance is unclear.
Dosing literature
Approved dosing (subcutaneous, once daily):
- HIV-associated lipodystrophy (Egrifta): 2 mg subcutaneous, once daily, abdominal injection rotation
- Egrifta SV (more concentrated formulation): 1.4 mg in smaller volume
Daily dosing is required because of the relatively short half-life. The injection burden is real — patients on long-term therapy report it as a meaningful tolerability factor.
Off-label body-composition protocols sometimes use the same 2 mg daily dose, sometimes lower (1 mg) or alternative-day dosing. None of these are based on RCT evidence.
Risks and adverse events
Common (FDA label, from Phase 3 data):
- Arthralgia (joint pain) — class effect of GH-axis stimulation
- Injection-site reactions — erythema, pruritus, irritation
- Peripheral edema
- Myalgia
- Paresthesia / hypoesthesia
- Carpal tunnel symptoms
Less common but important:
- Glucose intolerance / hyperglycemia — chronic GH elevation impairs insulin sensitivity. HIV-infected patients on antiretroviral therapy already have elevated diabetes risk; tesamorelin can compound it.
- Diabetic retinopathy worsening in patients with pre-existing retinopathy
- Theoretical malignancy risk — chronic IGF-1 elevation; the FDA label notes that tesamorelin should be used with caution in patients with active malignancy
For off-label users without clinical monitoring:
The HbA1c monitoring, lipid surveillance, and IGF-1 level checking that are part of clinical use don’t happen with self-sourced gray-market product. The risk profile is the same; the surveillance to catch problems early is absent.
Regulatory status
| Region | Status | Notes |
|---|---|---|
| United States | Approved (Egrifta, Egrifta SV) | For HIV-associated lipodystrophy only. |
| European Union | Approved | Same indication. |
| Canada | Approved | Same indication. |
| Australia | Approved | Same indication. |
| Japan | Not approved | |
| WADA | Prohibited (S2 — Peptide Hormones) | Banned in competitive sport at all times. |
Where to get it
For the approved indication, through a clinician with HIV-care experience and a specialty pharmacy. The drug is expensive (significant cost per month) and access is gated through specialty distribution.
For off-label use, the legitimate path is a clinician relationship and prescribed therapy with appropriate monitoring (HbA1c, IGF-1 levels, glucose, lipid panel). The gray-market “tesamorelin” sold by research-peptide vendors carries the same product-identity and quality concerns as other peptides in this category.
We have no fulfillment partner for tesamorelin at this time. (See How we make money.)
References (selected)
- Falutz J et al. Metabolic effects of a growth hormone-releasing factor in patients with HIV. N Engl J Med 2007. PubMed
- Falutz J et al. Long-term safety and effects of tesamorelin, a growth hormone-releasing factor analogue, in HIV patients with abdominal fat accumulation. AIDS 2008.
- Stanley TL et al. Effects of tesamorelin on visceral fat and liver fat in HIV-infected patients with abdominal fat accumulation. JAMA 2014.
- FDA prescribing information, Egrifta and Egrifta SV — current revisions.
Quick Facts
| Also Known As | TH9507, Growth Hormone-Releasing Factor (GRF) (1-44) amide, hGRF(1-44)NH2 |
|---|---|
| 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-Gln-Gln-Gly-Glu-Ser-Asn-Gln-Glu-Arg-Gly-Ala-Arg-Ala-Arg-Leu-NH2 |
| Molecular Formula | C221H366N72O67S |
| Molecular Weight | 5136 Da |
| PubChem CID | 16137828 |
Research Parameters
| Half-Life | ~26-38 minutes (terminal half-life after subcutaneous administration in humans) |
|---|---|
| Stability | Lyophilized powder is stable at recommended storage conditions for extended periods. After reconstitution with sterile or bacteriostatic water, the solution should be stored at 2-8°C. Stability after reconstitution is typically 28 days when refrigerated, though specific data should be confirmed from the manufacturer. |
| Solubility | Bacteriostatic Water for Injection or Sterile Water for Injection |
| Vial Size | 1 mg |
| Storage (Lyophilized) | -20°C, protect from light and moisture |
| Storage (Reconstituted) | 2-8°C (refrigerated), protected from light |
| Typical Research Dose | 2000 mcg (2 mg) |
| Cycle Parameters | In clinical research for its primary indication, administration was a daily subcutaneous injection, often continued for 6-12 months or longer in extension studies. Specific 'on/off' cycling protocols are not standard in the published literature for its approved use. |
| Amino Acid Count | 45 |
Mechanism of Action
Tesamorelin acts as a potent agonist of the growth hormone-releasing hormone receptor (GHRH-R) in the anterior pituitary gland. Its binding initiates a cascade of intracellular events leading to the synthesis and pulsatile secretion of endogenous growth hormone (GH), which in turn mediates its effects primarily through the stimulation of insulin-like growth factor 1 (IGF-1) production in the liver.
GHRH Receptor Activation: Tesamorelin binds with high affinity to the GHRH-R on somatotroph cells. This activates the Gs protein, stimulating adenylate cyclase and increasing intracellular cyclic AMP (cAMP) levels.
cAMP/PKA Pathway: Elevated cAMP activates protein kinase A (PKA), which phosphorylates transcription factors like CREB (cAMP response element-binding protein). This leads to increased transcription of the GH gene and subsequent synthesis of GH.
Growth Hormone and IGF-1 Axis: The pulsatile release of GH into the bloodstream acts on hepatocytes, stimulating the production of insulin-like growth factor 1 (IGF-1). The systemic effects of tesamorelin, such as the reduction of visceral adipose tissue and modulation of lipid metabolism, are largely mediated through this GH-IGF-1 axis.
Research Applications
Lipid Metabolism and Body Composition: Research has demonstrated that tesamorelin significantly reduces visceral adipose tissue (VAT) mass without substantially affecting subcutaneous fat. Studies in HIV-infected patients with lipodystrophy showed improved lipid profiles, including reduced triglycerides and increased HDL cholesterol, alongside decreased VAT. The mechanism is linked to GH-induced lipolysis and increased fatty acid oxidation.
Neurocognitive Function: Preliminary research has explored the potential cognitive benefits of tesamorelin, given the presence of GHRH receptors in the brain and the role of GH/IGF-1 in neuronal health. Some studies suggest it may improve executive function and memory in populations with growth hormone deficiency or mild cognitive impairment, though this remains an area of active investigation.
Metabolic Syndrome and Aging: Research has examined tesamorelin's effects on broader metabolic parameters associated with aging and obesity. Benefits include improvements in insulin sensitivity in some models, reduction in liver fat, and potential positive effects on cardiovascular risk markers, positioning it as a candidate for studying age-related metabolic decline.
Safety & Side Effects
In controlled clinical trials, the most common side effects reported were injection site reactions (erythema, pruritus, pain), arthralgia (joint pain), myalgia (muscle pain), peripheral edema, and paresthesia (tingling). As it stimulates GH secretion, theoretical concerns and some reported effects include glucose intolerance or increased insulin resistance, carpal tunnel syndrome, and potential exacerbation of pre-existing malignancies due to the mitogenic properties of IGF-1. These risks are considered manageable with appropriate monitoring. Anecdotal reports from research contexts are limited but align with the clinical trial profile.
Dosage Information
This information is derived from published clinical and preclinical research studies only and is not a recommendation for use.
In human clinical trials for HIV-associated lipodystrophy, the standard dose was 2 mg administered once daily via subcutaneous injection. The typical research dose range in these studies was fixed at 2 mg/day. Administration was subcutaneous, usually in the abdomen, with a daily frequency. Treatment duration in pivotal trials commonly ranged from 26 to 52 weeks.
References
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.
Falutz, J., Mamputu, J. C., Potvin, D., 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, 2010, 95(9), 4291-4304.
Stanley, T. L., Feldpausch, M. N., 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. JAMA, 2014, 312(4), 380-389.
Baker, L. D., Barsness, S. M., Borson, S., et al. Effects of growth hormone–releasing hormone on cognitive function in adults with mild cognitive impairment and healthy older adults: results of acontrolled trial. Archives of Neurology, 2012, 69(11), 1420-1429.
Mulligan, K., Khatami, H., Schwarz, J. M., et al. The effects of recombinant human growth hormone on hepatic lipid and carbohydrate metabolism in HIV-infected patients with fat accumulation. PLoS ONE, 2012, 7(8), e40106.
Svensson, J., Monson, J. P., Vetter, T., et al. The effect of subcutaneous tesamorelin on body composition and metabolic parameters in obese subjects. Growth Hormone & IGF Research, 2010, 20(3), 215-221.