Age Dependence of the Levels of Plasma Norepinephrine, Aldosterone, Renin Activity and Urinary Vanillylmandelic Acid in Normal and Essential Hypertensives
In the present study the upper reference limits (URLs) for resting plasma norepinephrine, epinephrine, serum aldosterone, plasma renin activity, aldosterone/ renin activity ratio, as well as urinary vanillylmandelic acid in healthy Egyptian normotensive subjects over a range of ages (5-60 yr) were established. There was a significant age effect on plasma norepinephrine, UVMA, serum aldosterone and PRA, whereas a single URL for plasma epinephrine level is satisfactory. In uncomplicated untreated essential hypertensive subjects (5-60 yr), the average prevalence of elevation in the plasma norepinephrine, epinephrine and urinary vanillylmandelic acid above their corresponding URLs was 85.10,62.15 and 83.20 %, respectively. This suggests that elevation in plasma catecholamine concentrations is more likely a common consequence than playing a possible role in the pathogenesis of hypertension, supported by insignificant correlation coefficients between the plasma catecholamine levels and resting systolic and diastolic blood pressure values (SBP&DBP) in all hypertensive age groups. Primary hyperaldosteronism was not detected among the normokalemic essential hypertensives at any age using aldosterone /plasma renin activity ratio as a primary screening method. In the present study, 7 statistically significant positive coefficient correlations are reported for SBP or DBP values with UVMA levels in hypertensive children and adolescents, serum aldosterone in old hypertensives, and PRA in adult hypertensives.