Low Levels of Renin and High Aldosterone-to-Renin Ratio Among Rheumatoid Patients and Ankylosing Spondylitis Patients: A Prospective Study.

BACKGROUND: Patients with rheumatic diseases, such as rheumatoid arthritis (RA) and ankylosing spondylitis (AS), encounter significantly higher rates of cardiovascular morbidity and mortality. The renin-angiotensin-aldosterone system maintains hemodynamic stability through blood pressure regulation. When dysregulated, this system has been implicated in various pathological conditions, including cardiovascular events.

OBJECTIVES: To investigate the levels of renin and aldosterone in RA and AS patients.

METHODS: Three groups were recruited: patients with RA, patients with AS, and healthy controls. Subjects were excluded if they had a diagnosis of hypertension, hyperaldosteronism, or renal artery stenosis, or were taking drugs that might have affected renin levels. Renin and aldosterone levels were measured using commercially available kits. Data were analyzed using univariate analyses and multivariate regression analyses.

RESULTS: Fifty-one subjects were enrolled in the study: 15 with RA, 4 with AS, and 32 healthy controls. At the univariate analysis, the three groups differed in age (P = 0.005), renin levels (P = 0.013), and aldosterone-to-renin ratio (P = 0.019). At the post-hoc tests, both AS and RA patients differed from controls for renin levels and the aldosterone-to-renin ratio. At the multivariate regression analysis, AS patients had lower renin values than controls (beta standardized regression coefficient -0.323, P = 0.022).

CONCLUSIONS: Patients with RA tended to have lower levels of plasma renin compared to healthy subjects. This finding indicates that the renin-angiotensin-aldosterone system might not be directly involved in the process that results in increased cardiovascular events in rheumatoid arthritis.