Background: The aldosterone-to-renin ratio (ARR) is frequently used to screen primary hyperaldosteronism. This study, part of a clinical trial, was designed to measure the influence of circadian rhythms, antihypertensive drugs, and body posture on plasma renin, on aldosterone, and on their interrelation.
Methods: In a prospective, randomized, open-label, parallel-designed protocol, 57 essential hypertensives (41 men, 16 women) were randomized to a morning dose of telmisartan (80 mg), ramipril (10 mg), or amlodipine (10 mg) for 8 weeks. At baseline and after 8 weeks of therapy, blood pressure (BP), plasma renin (in nanograms per liter), and plasma aldosterone (in picomoles per liter) concentrations were assessed in the supine position every 4 h for 24 h and after 10 min of standing at 9 am.
Results: There was no significant association between renin, aldosterone, the ARR and demographic factors, or BP. Circadian variations of plasma renin and aldosterone were clearly present. Aldosterone variations were of greater relative amplitude with earlier-occurring peaks than renin. The ARR exhibited statistically and clinically significant circadian variations with the low and peak values averaging 55.9 +/- 32.3 and 161.84 +/- 85.4 pmol/L/ng/dL, respectively. Telmisartan, ramipril, and amlodipine significantly decreased the ARR. Telmisartan had the greatest influence on the ARR. Posture had a clinically significant but statistically nonsignificant effect on the ARR.
Conclusions: Renin, aldosterone, and their interrelation are influenced by circadian rhythms, telmisartan, ramipril, and amlodipine in patients with essential hypertension. Telmisartan has a greater impact on these parameters than ramipril and amlodipine. Measurement of the ARR in treated hypertensive patients should take these influences into account.