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 (=0.287) and aldosterone (=-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 (=0.327), albumin (=-0.331), C-reactive protein (=0.317), ferritin (=0.473), and D-dimer (=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.