What tesamorelin is
Tesamorelin is a synthetic version of the first 44 amino acids of human growth-hormone-releasing hormone (GHRH), with a trans-3-hexenoyl group added to the N-terminus. That small modification is the whole point: native GHRH is degraded within minutes by the enzyme DPP-4, whereas tesamorelin resists it long enough to do its job. It is the only GHRH analog to have cleared a full regulatory review — the FDA approved it in 2010 as Egrifta for HIV-associated lipodystrophy, the abnormal accumulation of abdominal fat seen with certain antiretroviral regimens.
That regulatory history is what sets tesamorelin apart in the GH-peptide field. Most compounds in this space rest on preclinical data alone; tesamorelin carries double-blind, placebo-controlled human trials published in the highest-tier journals.
How tesamorelin works: releasing GH, not replacing it
The cleanest way to picture the mechanism is a thermostat versus a furnace. Injecting synthetic growth hormone is like running the furnace directly at a fixed setting — effective, but it overrides the body’s own controls. Tesamorelin instead nudges the thermostat: it signals the pituitary to release its ownGH in the natural pulsatile pattern, and the body’s feedback loops still decide how much.
Mechanistically, tesamorelin binds the GHRH receptor on pituitary somatotrophs and raises endogenous GH secretion, which in turn lifts hepatic IGF-1. Because the half-life is short — on the order of 26–38 minutes — the signal is a pulse, not a flood, and the negative-feedback machinery (somatostatin) stays in play. This is the pharmacological argument for why GHRH analogs are studied as a more physiological lever than exogenous GH.
The clinical data: visceral fat
The evidence base is unusually strong for a peptide. Two landmark publications anchor it:
| Study | Journal | Key finding |
|---|---|---|
| Falutz et al. (2007) | NEJM | Significant reduction in visceral adipose tissue; rise in IGF-1 |
| Stanley et al. (2014) | JAMA | Confirmed body-composition and metabolic-marker effects, including liver fat |
The pooled signal: roughly a 15% reduction in visceral adipose tissue over 26 weeks, with lower triglycerides and improved hepatic-fat markers, and — notably — no deterioration of fasting glucose, a common concern with direct GH. The effect was specific to visceral fat (the metabolically active depot wrapped around the liver, pancreas and intestines), not the subcutaneous fat under the skin. When treatment stopped, the fat returned, which is consistent with a signaling effect rather than a structural one.
Dosing as it appears in the literature
The approved clinical protocol is 2 mg once daily, subcutaneously, reflecting the short half-life. This describes a regulated, FDA-approved medical regimen in patients — it is reported here for context, not as a recommendation. Research-grade tesamorelin is supplied as a white lyophilized powder, reconstituted with bacteriostatic water for in-vitro work only and never for human use. The handling and concentration math are the same as any lyophilized peptide and are covered in the complete research peptides guide; the bacteriostatic water used as the diluent is in the catalog.
Tesamorelin vs CJC-1295 vs ipamorelin
These three are often grouped together but do not work the same way. Two are GHRH analogs; one is not.
| Peptide | Pathway | Distinguishing point |
|---|---|---|
| Tesamorelin | GHRH analog (44 aa) | FDA-approved; strongest visceral-fat evidence |
| CJC-1295 | GHRH analog | Longer-acting variant; versatile research tool |
| Ipamorelin | GHRP / ghrelin-receptor agonist | Different receptor; selective, spares cortisol & prolactin |
Because GHRH analogs and GHRPs act on separate receptors, CJC-1295 and ipamorelin are frequently combined in research models to probe additive GH release. Tesamorelin remains the reference compound when the research question is specifically about visceral fat, for the simple reason that it has the trial data nothing else in the class can match.
Storage and handling
As a lyophilized peptide, tesamorelin is stable for roughly 18 months sealed at −20 °C. After reconstitution it should be refrigerated at 2–8 °C and used within about four weeks, protected from light. For purity benchmarks (>99% HPLC), Certificate-of-Analysis checks and storage across the catalog, the research peptides guide is the foundational reference; researchers studying metabolic pathways may also look at NAD+ and MOTS-c in the same context.