Clinical Utility of the Ratio of Urinary Free Cortisol to Aldosterone as an Index for Inflammatory and Metabolic Dysregulation

OBJECTIVE: Urinary free cortisol (UFC) is a reliable marker to avoid cortisol fluctuation and the effects of binding proteins. However, UFC levels are affected by fluid intake and urine volume, and the normal levels range widely. METHODS: To discover the utility of the ratio of urinary cortisol to aldosterone excretions, 246 patients in whom daily excretions of UFC and aldosterone (UAC) were measured were retrospectively analyzed. RESULTS: The UFC/UAC ratio showed significant positive and negative correlations with the levels of serum cortisol (R=0.287) and aldosterone (R=-0.762), respectively. The UFC/UAC ratio increased with aging in female patients, while it was not altered by the level of BMI in either gender. Markers for metabolic and inflammatory status, including hemoglobin A1c (R=0.327), albumin (R=-0.331), C-reactive protein (R=0.317), ferritin (R=0.473), and D-dimer (R=0.569), showed correlations with the ratio of UFC/UAC that were more significant than the correlations with the serum level of cortisol or UFC alone. Of note, the UFC/UAC ratio was shown to be an indicator for the risk of diabetes (AUC: 0.765), hypoalbuminemia (0.839), hyper-CRPemia (0.748), and thrombophilia (0.824), in which the cut-off levels of the UFC/UAC ratio were around 12. CONCLUSION: The UFC/UAC ratio is a variable for detecting metabolic and inflammatory complications related to adrenocortical dysfunction.