THE ENDOCRINOLOGY OF AGING

Most aging individuals die from atherosclerosis: cancer, or dementia; but in the oldest old, loss of muscle strength resulting in frailty is the limiting factor for an individual's chances of living an independ ent life until death. Three hormonal systems show decreasing circulati ng hormone concentrations during normal aging: (i) estrogen (in menopa use) and testosterone (in andropause), (ii) dehydroepiandrosterone and its sulphate (in adrenopause), and (iii) the growth hormone/insulin-l ike growth factor I axis (in somato-pause). Physical changes during ag ing have been considered physiologic, but there is evidence that some of these changes are related to this decline in hormonal activity. Hor mone replacement strategies have been developed, but many of their asp ects remain controversial, and increasing blood hormone levels In agin g individuals to those found during mid-adult life has not been unifor mly proven to be safe and of benefit.