What is tesamorelin?
Tesamorelin contains the full 44-amino-acid sequence of human GHRH with one change: a small fatty chemical group, called a trans-3-hexenoyl group, attached to the front end. That change helps protect it from the enzymes that quickly break down natural GHRH, so it stays active longer. It was developed by the Canadian company Theratechnologies under the code name TH9507.
In its approved use, tesamorelin is given as an injection to reduce excess fat around the abdominal organs in adults with HIV who developed lipodystrophy, a shift in body fat linked to some HIV treatments. It was not developed as a general weight-loss drug, and its main effect in trials was on deep belly fat. Researchers have also studied it for fatty liver and for thinking skills in older adults.
How does tesamorelin work?
Tesamorelin binds to GHRH receptors on growth hormone-making cells in the pituitary gland. This prompts them to make and release more growth hormone, which raises IGF-1 from the liver. Growth hormone encourages fat cells, particularly the deep visceral fat around the organs, to release stored fat. Because tesamorelin works through the pituitary rather than replacing the hormone, somatostatin and IGF-1 feedback still shape the response, and studies found that the normal pulsing pattern of growth hormone was kept.
Tesamorelin vs other GHRH peptides
Several peptides act on the same GHRH receptor. Sermorelin is the first 29 amino acids of GHRH and acts for only minutes. MOD-GRF 1-29, often called CJC-1295 without DAC, is the same 29-amino-acid stretch with four amino acid swaps that slow its breakdown. CJC-1295 with DAC adds a linker that binds to blood proteins, stretching its action to about a week. Tesamorelin is the full-length hormone with a protective group. Its main distinction is evidence: it is the only one of these with large placebo-controlled trials in adults.
What has research looked at?
Tesamorelin has stronger human evidence than most compounds in this library, but nearly all of it comes from people with HIV. Claims about muscle building, anti-aging or nerve repair in healthy adults go beyond what has been studied so far, and long-term data outside HIV are limited.
- Visceral fat in HIV
- Two large placebo-controlled trials in adults with HIV-associated lipodystrophy found that tesamorelin reduced visceral fat measured on CT scans. Much of the reduction was lost after treatment stopped.
- Liver fat
- Randomized trials in people with HIV reported less fat in the liver than with placebo, and one suggested slower progression of liver scarring.
- Cognition in older adults
- A randomized trial in older adults, including people with mild cognitive impairment, reported better scores on tests of executive function than placebo. It was a single trial, so the finding needs confirmation.
- Blood fats
- The HIV trials also reported modest improvements in triglycerides compared with placebo.
- Obesity without HIV
- Smaller studies have looked at people with abdominal obesity who do not have HIV, but this research is limited.
Side effects and cautions
Because tesamorelin went through large trials, its side effects are fairly well described. Most relate to higher growth hormone and IGF-1 or to the injection itself, and IGF-1 is typically monitored in clinical care. Its approved labeling advises against use in pregnancy, in active cancer and in people whose pituitary system has been disrupted by surgery, tumors or radiation, and a past history of cancer calls for careful review. Talk to a qualified clinician about any growth hormone-related treatment.
- Joint and muscle pain
- Joint pain, pain in the arms or legs and muscle aches were among the most common effects in trials.
- Injection-site reactions
- Redness, itching, pain or irritation where it is injected were common.
- Fluid retention
- Swelling of the hands or feet and carpal tunnel-type symptoms can occur.
- Blood sugar
- It raised blood sugar in some trial participants and can reduce insulin sensitivity, so people with diabetes need closer monitoring.
- Allergic reactions
- Rash, hives and other hypersensitivity reactions have been reported, and some people develop antibodies to tesamorelin.
Further reading
This page summarizes the research in plain words. To read the studies yourself:
- Published studies on Tesamorelin PubMed, US National Library of Medicine
- Registered human trials of Tesamorelin ClinicalTrials.gov
