The injection makes the body produce more of a natural growth-related hormone called IGF-1, which helps explain how it reduces belly fat.

The drug makes the body produce more IGF-1 — a hormone linked to growth and metabolism — which is exactly what you’d expect from a drug that stimulates growth hormone.

Tesamorelin boosts a key growth hormone-related protein in HIV patients without affecting their blood sugar levels.

The drug shrinks the fat around the torso and makes the waist smaller, but doesn’t change the fat on the arms, legs, or just under the skin — meaning it targets only the dangerous internal fat.

People with HIV who have belly fat and are on medication to control the virus who took tesamorelin had higher levels of a growth-related hormone called IGF-1. This finding is from the abstract summary - full study details were not available

Rising IGF-1 levels helped explain some of the muscle growth from the drug, but not all of it—so other factors are also at work.