Mineralocorticoid Receptor Antagonist Effect on Aldosterone to Renin Ratio in Patients with Primary Aldosteronism

Context: Although current international guidelines recommend to avoid mineralocortcoid receptor antagonists in patients undergoing screening test for primary aldosteronism, a recent report suggested that mineralocorticoid receptor antagonist treatment can be continued without significant influence on screening results. Objective: We aimed to evaluate the effect of mineralocorticoid receptor antagonists on the aldosterone to renin ratio in patients with primary aldosteronism. Methods: We prospectively enrolled 121 patients with confirmed primary aldosteronism who started mineralocorticoid receptor antagonist (canrenone) treatment. Eighteen patients (11 with unilateral and 7 with bilateral primary aldosteronism) constituted the short-term study cohort and underwent aldosterone, renin, and potassium measurement after 2 and 8 weeks of canrenone therapy. The long-term cohort comprised 102 patients (16 with unilateral and 67 with bilateral primary aldosteronism, and 19 with undetermined subtype) who underwent hormonal and biochemical re-assessment after 2 to 12 months of canrenone therapy. Results: Renin and potassium levels showed a significant increase, and the aldosterone to renin ratio displayed a significant reduction compared with baseline after both a short-and long-term treatment. These effects were progressively more evident with higher doses of canrenone and after longer periods of treatment. We demonstrated that canrenone exerted a deep impact on the diagnostic accuracy of the screening test for primary aldosteronism: the rate of false negative tests was raised to 16.7%, 38.9%, 54.5%, and 72.5% after 2 weeks, 8 weeks, 2 to 6 months, and 7 to 12 months of mineralocorticoid receptor antagonist treatment, respectively. Conclusion: Mineralocorticoid receptor antagonists should be avoided in patients with hypertension before measurement of renin and aldosterone for screening of primary aldosteronism.