Tesamorelin

What tesamorelin is and how it works

Most GHRH analogues are built on the first 29 residues of the hormone, the shortest piece that still activates the receptor. Tesamorelin is not. It is the complete 44-amino-acid sequence of human growth-hormone-releasing hormone with one addition: a trans-3-hexenoyl group attached to the tyrosine at the N-terminus. That small fatty acyl chain shields the peptide from dipeptidyl peptidase-4, the enzyme that otherwise clips native GHRH in half within minutes. It was developed in Canada under the code TH9507 and reached the market as Egrifta.

The receptor is the GHRH receptor on somatotroph cells in the anterior pituitary. Occupying it raises cyclic AMP, which drives both synthesis of growth hormone and release of what the cell has stored. Working at this level rather than injecting growth hormone directly leaves the regulatory loops in place: somatostatin still applies the brake, IGF-1 still feeds back, and the trials found that the pulsatile pattern of secretion was preserved. Output rises, but the shape of the signal stays close to the body's own.

The indication grew out of a specific clinical problem. People with HIV on long-term antiretroviral treatment can accumulate visceral fat, the depot around the organs, and blunted growth hormone secretion is part of that picture. Growth hormone is lipolytic and visceral fat responds to it, so the reasoning was to restore the body's own output rather than to replace the hormone. That is the question the trials asked, and it is narrower than the way tesamorelin is often discussed.

What the research on tesamorelin shows

The evidence base is unusual for a peptide of this kind: randomised, double-blind, placebo-controlled phase 3 trials with an imaging endpoint. Adults with HIV and excess abdominal fat received 2 mg once daily by subcutaneous injection for 26 weeks, with visceral adipose tissue measured by CT. Visceral fat fell by roughly 15% while it rose slightly on placebo; the first of these trials was published in the New England Journal of Medicine in 2007. Subcutaneous fat was largely unaffected, which is the point of the result.

IGF-1 was watched throughout. Raising growth hormone raises IGF-1, the growth factor that carries much of the downstream action, and in the trials some participants moved above the normal range. That is why the approved product is used with IGF-1 measurement, and why glucose was followed closely in a population already prone to insulin resistance.

What the trials did not settle

The benefit depends on continued treatment: visceral fat returned once dosing stopped. Beyond the licensed indication, a randomised trial in people with HIV and fatty liver disease reported a reduction in liver fat (Lancet HIV, 2019). There is no trial evidence for tesamorelin as a general fat-loss agent in people without HIV, none for athletic performance, and none for the ageing-related uses it is sometimes advertised for.

Doses of tesamorelin used in published research

These figures describe one authorised indication in one patient group, under medical supervision and with laboratory monitoring. They are the schedules of published trials and of a licensed product, not instructions, and they say nothing about anyone outside that group.

Safety and side effects of tesamorelin

Because an approved product exists, the safety picture is better documented than for the rest of this class; the findings below come from the clinical programme and the US label.

• Injection-site reactions. Redness, itching and local pain were among the most frequently reported effects in the trials.
• Joint pain and fluid retention. Arthralgia, muscle pain and swelling in the limbs are recognised consequences of raising growth hormone output and were seen in the programme.
• Raised IGF-1. Some participants exceeded the normal range. The label advises measuring IGF-1 and reconsidering treatment when it stays high, which is the standard approach wherever a therapy lifts this axis.
• Glucose intolerance. Growth hormone opposes insulin. The label carries a warning about worsening glucose control, relevant in a population with a high background rate of insulin resistance.
• Hypersensitivity. Rash and urticaria are described, as with other injected peptides.
• Cell proliferation. Because the GH and IGF-1 axis drives growth, the label warns against use in people with active malignancy.

Regulatory status of tesamorelin in Europe

Tesamorelin holds a US approval, granted in 2010, for the reduction of excess abdominal fat in HIV-associated lipodystrophy. It has no marketing authorisation in the European Union. There is no EMA-approved product and no European summary of product characteristics, so the medicine that exists in the United States is not available as one here. Anything sold in Europe under this name is research material: unlicensed and not for human use. Rules on possession and personal import are national, not EU-wide.

In sport, GHRH analogues including tesamorelin fall under section S2 of the WADA Prohibited List, banned at all times, in and out of competition. The way it compares with the ghrelin-receptor agonists is set out in our guide to growth hormone secretagogues.

Sourcing and quality: tesamorelin for research

King Peptides lists this peptide as Tesamorelin 10 mg, an exact match for this profile rather than a substitute. Chain length is the quality issue here. At 44 residues, tesamorelin is far longer than the five-residue secretagogues, and long peptides accumulate deletion and truncation by-products during synthesis. Those by-products are chemically similar to the target, so they show up as shoulders and satellite peaks rather than as obvious contamination. Read the chromatogram for a purity figure of at least 99% by HPLC, then check that the reported mass sits at the 5135.9 Da in the panel. A certificate whose lot number does not match the vial in your hand documents a different batch of material, however clean it looks.

Orders are dispatched from the Netherlands, inside the EU, and every lot carries its own certificate with HPLC and mass spectrometry results. Delivery usually takes 1–2 business days within the Netherlands and 3–5 business days elsewhere in the EU on the shop's own estimate, with no customs inside the union; shipments to the UK, Switzerland, Norway and other non-EU destinations can attract import rules and duties. Packaging is neutral and tracked, and buyers confirm at checkout that they are ordering for research and are 18 or older. Our guides to reading a certificate of analysis and to storage and reconstitution explain the rest.

Tesamorelin frequently asked questions

Can a doctor in the EU prescribe tesamorelin? Not as an authorised medicine. Egrifta is a US product and the EU has granted no authorisation, so no European pharmacy dispenses it as a licensed treatment.

Is research tesamorelin the same thing as Egrifta? The peptide is the same molecule by name. The product is not: a research vial has no marketing authorisation, no regulated manufacturing dossier behind it and no clinical oversight. Its certificate of analysis is the only statement about what it contains.

Does tesamorelin reduce fat in people without HIV? That question has not been answered by the trials, which studied a specific population with a specific pattern of fat accumulation. Extending the result to anyone else is an assumption.

How does it differ from CJC-1295? Length and duration. Tesamorelin is the full 44-residue hormone acting for well under an hour, given daily; CJC-1295 with DAC is a 29-residue fragment tethered to albumin that acts for days. One holds an approval; the other was discontinued in development.