Three hormonal systems show decreasing circulating hormone concentrations during normal aging : (1) estrogen(in menopause), and testosterone (in andropause), (2) dehydroepiandrosterone and its sulfate (in adrenopause), and (3) the growth hormone/insulin-like growth factor 1 axis (in somatopause). Throughout the adult life, all physiological functions gradually decline. There is a diminishing capacity for cellular protein synthesis, an decline in immune function, an increase in fat mass, a loss of muscle mass and strength, and a decrease in bone mineral density. Physical changes during aging have been considered physiologic, but there is evidence that some of these changes are related to the decline in the hormonal activity. Various hormonal replacement strategies have been developed, but many of their aspects remain controversial, and increased blood hormone levels in aging individuals to those found during the mid-adult life have not been uniformly proven to be safe and of benefit.