Context Primary aldosteronism (PA) represents the most frequent form of endocrine hypertension. Hyperaldosteronism and hypercortisolism both induce excessive left ventricular hypertrophy (LVH) compared to matched essential hypertensives. In recent studies frequent co-secretion of cortisol and aldosterone has been reported in PA patients. Objective Our aim was to investigate the impact of cortisol co-secretion on left ventricular hypertrophy in PA patients. We determined 24-h excretion of mineralocorticoids and glucocorticoids by gas chromatography-mass spectrometry and assessed cardiac remodeling using echocardiography initially and one year after initiation of treatment for PA. Patients We included 73 patients from the Munich center of the German Conn's registry; 45 with unilateral aldosterone-producing adenoma and 28 with bilateral adrenal hyperplasia. Results At the time of diagnosis, 85% of PA patients showed left ventricular hypertrophy according to left ventricular mass index (LVMI, median 62.4 g/m2.). LVMI correlated positively with total glucocorticoid excretion (r2=0.076, p=0.018) as well as with tetrahydroaldosterone excretion (r2=0.070, p=0.024). Adrenalectomy led to significantly reduced LVMI in aldosterone-producing adenoma (p<0.001) while mineralocorticoid receptor antagonist therapy in bilateral adrenal hyperplasia patients reduced LVMI to a lesser degree (p=0.024). In multivariate analysis, the decrease in LVMI was positively correlated with total glucocorticoid excretion and systolic 24-hour blood pressure, but not with tetrahydroaldosterone excretion. Conclusion Cortisol excess appears to have an additional impact on cardiac remodeling in patients with PA. Treatment of PA by either adrenalectomy or mineralocorticoid receptor antagonist improves LVMI. This effect was most pronounced in patients with high total glucocorticoid excretion.