Association Between Serum Cortisol and Chronic Kidney Disease in Patients with Essential Hypertension

Background/Aims: Serum cortisol level is elevated in patients with essential hypertension. We aimed at investigating the association of serum cortisol levels with parameters of renal function in essential hypertension. Methods: One hundred and seventy-eight patients with essential hypertension participated in the study. Fasting serum samples were collected at 8:00 am. Renal function was measured as estimated glomerular filtration rate (eGFR) calculated by the Chronic Kidney Disease Epidemiology Collaboration creatinine- cystatin C equation (eGFRcr-cys). Correlation analysis and stepwise regression analysis were used to detect the relationship between cortisol and eGFRcr-cys. The distributions of serum cortisol were split by the tertiles and subjects were stratified into those with low, median and high levels accordingly. Results: Serum cortisol levels were significantly higher in subjects whose eGFRcr-cys<90 ml/min/1.73 m² than subjects whose eGFRcr-cys>90 ml/min/1.73 m² (394.0±93.4 vs. 343.2±98.4 nmol/L, P=0.001). Age, systolic blood pressure, and serum total cholesterol, uric acid, cortisol levels were significantly associated with eGFRcr-cys, serum levels of creatinine and cystatin C. After adjusting for clinical factors, serum cortisol level had a statistically significant negative association with the eGFRcr-cys (β=-0.19, P =0.027), and positive associations with cystatin C (β=0.31, P =0.001) and creatinine (β=0.14, P =0.044). With the increment of cortisol tertile, the eGFRcr-cys significantly decreased (93.18±14.36 vs. 84.61±14.67 vs. 81.29±12.36 ml/min/1.73 m² for low, median and high tertile, respecively, P=0.001). Conclusion: Serum cortisol level was negatively correlated with eGFRcr-cys in subjects with essential hypertension. Further studies are needed to investigate whether cortisol plays a role in hypertensive nephropathy development.