GH therapy has been implicated in the health of the endothelium and increases nitric oxide production in in vitro studies. In humans with GHD, short-term treatment has been shown in various studies to increase cardiac mass, decrease carotid intimal medial thickness, reverse early atherosclerotic changes in major arteries, and possibly improve the vasodilatory function of the endothelium. However, the hypertrophic effect of long-term replacement with GH appears to subside over time. It remains to be seen if GH replacement therapy will reduce the prevalence of cardiovascular disease in this population.