The secretion of growth hormone and testosterone declines with age. Because these hormones have prominent anabolic effects on skeletal muscle, part of the age-related decrease in muscle mass and strength have been attributed to declining levels of these hormones; however, growth hormone replacement in healthy elderly people has produced side effects but no functional benefit. In contrast, short-term growth hormone and insulin-like growth factor 1 treatment have reduced protein loss and improved function during acute catabolic states. Although testosterone replacement has increased lean body mass and improved the sense of well being, functional benefit has not been clearly demonstrated, and the risks of long-term replacement have not been defined.