The Role of Cortisol/ACTH Ratio for Screening of Subclinical Hypercortisolism in Patients with Adrenal Incidentalomas.

INTRODUCTION: The cortisol/ACTH ratio was supposed to be helpful in the screening of subclinical hypercortisolism (SHC) in the published literatures. This study assessed the cortisol/ACTH ratio in patients with adrenal incidentaloma (AI) confirmed to have SHC and investigated its role for screening SCS in patients with AI.

METHODS: This descriptive retrospective study included 183 patients with AIs [45 with SHC and 138 with non-functional adenoma (NFA)]. Cortisol and ACTH levels were measured at 8:00, 16:00, and 0:00, and the cortisol/ACTH ratio was calculated. ROC curve was used to evaluate efficacy of the cortisol/ACTH ratio, explore the best cut-off value and its corresponding sensitivity and specificity.

RESULTS: The cortisol/ACTH ratios at all time points were significantly higher in the SHC group than the NFA group (P<0.05) and were significantly correlated with serum cortisol levels after the 1-mg dexamethasone suppression test (DST). Area Under the Curve (AUC) of the cortisol/ACTH ratio at 0:00 and midnight serum cortisol levels were 0.893 (0.843-0.943) and 0.831 (0.765-0.806), respectively. A cortisol/ACTH ratio at 0:00 cut-off of 32.18 nM/pM showed a sensitivity of 100% and specificity of 39.1%. The optimal cut-off was 68.83 nM/pM (sensitivity 86.7%, specificity 75.4%).

CONCLUSIONS: Patients with SHC have a higher cortisol/ACTH ratio than those with NFAs. The cortisol/ACTH ratio is significantly correlated with serum cortisol after the 1-mg DST. The diagnostic performance of the cortisol/ACTH ratio at 0:00 is superior to midnight serum cortisol. Therefore, the cortisol/ACTH ratio at 0:00 may be a reliable parameter for SHC screening in patient with AI.