Interrelations between age and plasma renin, aldosterone and cortisol, urinary catecholamines, and the body...

Interrelations between age and plasma renin, aldosterone and cortisol levels, urinary catecholamiens, plasma and blood volumes, exchangeable body sodium and blood pressure wwere studied in 28 young (19 to 29 years), 16 middle-aged (32 to 58 years) and 15 elderly (60 to 74 years) healthy subjects. Supine and upright plasma renin and supine aldosterone levels decreased while urinary noradrenaline excretion rate increased progressively with aging (r= greater than 0.34; p less than 0.05), with significant differences in mean values between young and elderly subjects (p less than 0.02). There was also an age-related decrease in upright plasma aldosterone concentration, although this was no statistically significant. Furthermore, mean plasma cortisol concentrations increased in response to upright posture in elderly ( + 50%; p less than 0.02), but not in young ( --10%) or middle-aged ( --8%) subjects. Blood pressure correlated with age ( r =0.35; p less than 0.05) or noradrenaline excretion rate ( r= 0.34) in the entire study population and with blood volume in the elderly ( r = 0.68), but not in the young or middle-aged study. Groups. There were no significant age-related differences in the body sodium/volume state, basal plasma cortisol levels or urinary adrenaline excretion rate, and plasma renin or aldosterone levels did not correlate with these parameters or with blood pressure. It is concluded that the influence of age on plasma renin or aldosterone levels, plasma cortisol responsiveness to upright posture, and urinary noradrenaline excretion should be taken into consideration, whenever these factors have to be interpreted in patients with arterial hypertension or other clinical disorders. Further more, these data are conssitent with the possiblity that in normal man increases in supine blood pressure with aging may be related at least partly to concomitant changes in free peripheral noradrenaline.