Effects of growth hormone on adipose tissue.

Physiological effects of growth hormone (GH) extend beyond the stimulation of linear growth. These include important metabolic effects upon adipose tissue. GH affects both proliferation and differentiation of preadipocytes, although this varies between clonal cell lines and preadipocyte cultures. Both preadipocytes and mature adipocytes possess specific GH receptors. GH may mediate its actions via these receptors, but some effects are indirectly mediated through the GH-mediated secretion of insulin-like growth factor-I (IGF-I) within adipose tissue. GH promotes lipolysis via inhibition of lipoprotein lipase, which hydrolyzes triglycerides in the circulation to make them available for triglyceride accumulation in adipose tissue. GH also stimulates hormone sensitive lipase (HSL), the rate-limiting step for release of stored triglyceride in adipocytes (lipolysis). As GH becomes utilized for various "non-growth" concerns (see Figure 1), awareness of the metabolic effects on adipocytes is important to understand the clinical effects seen with GH therapy.