Urinary catecholamines in essential hypertension: results of 24-hour urine catecholamine analyses from patients in the Medical Research Council trial for mild hypertension and from matched controls.

Four consecutive 24-h urine samples were collected from 134 male and 134 female placebo-treated patients in the Medical Research Council Trial for Mild Hypertension. Similar samples were collected from age and sex-matched normotensive controls. On the fourth day noradrenaline excretion was 22.05 +/- 1.01 nmol/mmol creatinine in the hypertensives compared with 22.22 +/- 1.16 nmol/mmol creatinine in the controls. Adrenaline excretion on the same day was 6.13 +/- 0.33 nmol/mmol creatinine in the hypertensive subjects compared with 6.32 +/- 0.38 nmol/mmol creatinine in the controls. There was no significant difference for either catecholamine between the two groups. However, in the control group there was a highly significant correlation between excretion of adrenaline and systolic blood pressure (r = 0.218, p = 0.0004) and between noradrenaline excretion and systolic blood pressure (r = 0.200, p = 0.001). Catecholamine excretion and blood pressure were not significantly correlated in the hypertensive patients. There were no significant correlations in either group between catecholamine excretion and heart rate, caffeine intake, nicotine consumption or the Bortner self-assessment score of personality type. This study has found no evidence of elevated sympathoadrenal activity in mild hypertensives. The correlations in the control group may reflect the role of sympathoadrenal activity in acute fluctuations in blood pressure or may suggest that the level of blood pressure within the 'normal' range depends in part on the level of sympathoadrenal activity.