Tesamorelin

Growth hormone-releasing hormone is the body's own instruction to release growth hormone from the pituitary gland, and Tesamorelin is a laboratory-made version of that signal. Built from 44 amino acids with an added chemical group, it is approved in the United States for a specific condition involving abnormal fat buildup linked to HIV treatment. In trials it reduced visceral fat, the fat that surrounds internal organs, while leaving fat just under the skin largely untouched, a selective pattern researchers describe as unusual among growth-hormone-based treatments.

What it is

The body already makes growth hormone-releasing hormone as part of a natural signaling chain: the hormone signals the pituitary gland into releasing growth hormone, which then shapes metabolism and tissue growth throughout the body. Tesamorelin copies that natural hormone closely enough to bind the same pituitary receptor and trigger the same release, but with a chemical modification that keeps it active in the body longer than the natural version.

What distinguishes tesamorelin in the research literature is where its effect concentrates. Rather than reducing body fat broadly, trials in people with HIV-associated lipodystrophy, a condition marked by abnormal fat redistribution, found it selectively lowered visceral fat around the internal organs while sparing subcutaneous fat just beneath the skin. That selective pattern is the basis for its approved use and for continued research into its effects on liver fat and inflammation markers.

How it is studied

Tesamorelin has been studied mainly in placebo-controlled human trials in adults with HIV-associated lipodystrophy, typically over periods of 26 weeks to 12 months, measuring visceral fat by imaging alongside blood markers of inflammation and liver health. Because it is built on a natural pituitary-signaling hormone, the underlying pharmacology is well characterized from decades of growth hormone research, but tesamorelin's own trial record is concentrated in this one patient population rather than in the general public.

What studies report

Over 12 months, tesamorelin was linked to a roughly 37 percent reduction in liver fat and prevented the progression of liver scarring in people with HIV and a related fatty liver condition. [3]
A 12-month analysis found tesamorelin was associated with reductions in several inflammatory blood markers, described by researchers as effects that went beyond its fat-reduction action alone. [2]

What is not known

Tesamorelin's approved use and most of its trial record are specific to HIV-associated lipodystrophy, so its effects in people without that condition, including any broader claims about metabolism or body composition circulating outside the approved indication, have not been established by the same level of trial evidence. Questions about long-term use beyond about a year, and about how its selective fat-reduction effect compares with newer metabolic medicines, remain open in the published record.

Reported adverse findings

Trials reported that a substantial share of participants, nearly half by 26 weeks in some analyses, developed insulin-like growth factor 1 levels above the normal range, prompting a recommendation for regular monitoring. [3]
Common reported reactions included pain or irritation at the injection site and joint discomfort, alongside a documented increase in the risk of developing diabetes during treatment. [3]

Regulatory status

Tesamorelin, marketed under the brand name Egrifta, is approved by the United States Food and Drug Administration specifically for reducing excess visceral fat in adults with HIV-associated lipodystrophy. It is not approved for weight loss, muscle building, or anti-aging use in the general population.