GH-Mediated Lipolysis

Growth hormone is a lipolytic hormone, increasing the activity of hormone-sensitive lipase and adipose triglyceride lipase in the adipocyte while suppressing lipoprotein lipase mediated fat uptake. Its kinetics distinguish it from catecholamines: adrenergic lipolysis begins in minutes, whereas the growth hormone effect requires transcription and appears two to three hours after a pulse. This is why nocturnal pulses matter physiologically, mobilising fat during the overnight fast and sparing protein, and why deficiency produces a characteristic accumulation of visceral fat that replacement partially reverses.

The clearest human quantification comes from tesamorelin, a GHRH analogue approved in 2010 for excess visceral abdominal fat in HIV-associated lipodystrophy. In its registration trials, roughly six months of treatment reduced visceral adipose tissue on CT by a mid-teens percentage against placebo, with little effect on subcutaneous fat, and the visceral fat returned after treatment stopped.

It changes a decision mainly by clarifying what kind of endpoint is on offer. Visceral adipose tissue is a meaningful surrogate, associated with hepatic steatosis and cardiometabolic risk. But no trial has shown that moving it this way changes cardiovascular events or mortality, the effect is not maintained after discontinuation, and it is modest relative to what energy deficit achieves.

The error that follows people is treating fat mobilisation as free of cost. The free fatty acids released are the same molecules that blunt muscle glucose uptake, so the lipolysis and the insulin resistance are one mechanism, not a benefit with an unrelated side effect. A second misreading is scale weight in the first weeks, where sodium and water retention frequently offsets any fat loss, and the flat number gets attributed to muscle gain.