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.