Urinary catecholamines and the relationship with blood pressure and pharmacological therapy

Objectives: Our aim was to assess the importance of the sympathetic nervous system as assessed by urinary catecholamine measurement in the aetiology of essential hypertension and the importance of antihypertensive therapy in the excretion of urinary catecholamines. Methods: Twenty-four-hour urinary catecholamine measurement was performed in 1925 patients who were referred for treatment of hypertension and grouped according to the Sixth Report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure classification: of the 655 untreated patients, 59 were normotensive individuals (SBP < 140 and DBP < 90mmHg), n=219 stage 1 (SBP 140-159 or DBP 90-99mmHg), n=236 stage 2 (SBP 160-179 or DBP 100-109mmHg) and n=141 stage 3 (SBP ≥ 180 or DBP ≥ 110mmHg). Results: There was a statistically significant positive relationship between 24-h urinary norepinephrine excretion and the severity of hypertension, such that the higher the blood pressure the higher the urinary norepinephrine excretion (mean±standard error of mean): normotensive group, 221±13nmol/24h; stage 1, 254±8nmol/24h; stage 2, 263±7nmol/24h and stage 3, 296±12nmol/24h (P<0.001). The above relationship remained highly significant when corrected for urinary creatinine, weight, age and sex. No differences were found with urinary epinephrine or dopamine excretion. Urinary norepinephrine excretion was increased in those patients taking single-drug therapy with either a long-acting dihydropyridine calcium antagonist or a β-blocker. Conclusion: Our results demonstrate that in untreated hypertensive patients, urinary norepinephrine excretion is increased in proportion to the severity of blood pressure rise and also in patients taking a long-acting dihydropyridine calcium antagonist or a β-blocker. Sympathetic overactivity may play a role in the aetiology and maintenance of essential hypertension.