Blockade of the MR (mineralocorticoid receptor) in CKD (chronic kidney disease) reduces LVMI [LV (left ventricular) mass index] and proteinuria. The MR can be activated by aldosterone, cortisol and DOC (deoxycorticosterone). The aim of the present study was to explore the influence of mineralocorticoids on LVMI and proteinuria in patients with CKD. A total of 70 patients with CKD and 30 patients with EH (essential hypertension) were recruited. Patients underwent clinical phenotyping; biochemical assessment and 24 h urinary collection for THAldo (tetrahydroaldosterone), THDOC (tetrahydrodeoxycorticosterone), cortisol metabolites (measured using GC-MS), and urinary electrolytes and protein [QP (proteinuira quantification)]. LVMI was measured using CMRI (cardiac magnetic resonance imaging). Factors that correlated significantly with LVMI and proteinuria were entered into linear regression models. In patients with CKD, significant predictors of LVMI were male gender, SBP (systolic blood pressure), QP, and THAldo and THDOC excretion. Significant independent predictors on multivariate analysis were THDOC excretion, SBP and male gender. In EH, no association was seen between THAldo or THDOC and LVMI; plasma aldosterone concentration was the only significant independent predictor. Significant univariate determinants of proteinuria in patients with CKD were THAldo, THDOC, USod (urinary sodium) and SBP. Only THAldo excretion and SBP were significant multivariate determinants. Using CMRI to determine LVMI we have demonstrated that THDOC is a novel independent predictor of LVMI in patients with CKD, differing from patients with EH. Twenty-four hour THAldo excretion is an independent determinant of proteinuria in patients with CKD. These findings emphasize the importance of MR activation in the pathogenesis of the adverse clinical phenotype in CKD.