Beyond cortisol: multiplex steroid profiling after overnight dexamethasone suppression to optimize Cushing's syndrome screening.

PURPOSE: Cushing’s syndrome (CS) is a life-threatening endocrine disorder challenging to diagnose. The 1 mg Dexamethasone Suppression Test (DST) is highly sensitive but limited by specificity. This study evaluated the diagnostic value of liquid chromatography-tandem mass spectrometry (LC-MS/MS)-based post-DST serum steroid profiling in improving the discrimination between overt CS and non-CS conditions, providing enhanced diagnostic resolution for mild autonomous cortisol secretion (MACS).

METHODS

We prospectively analyzed paired pre- and post-DST serum from 232 patients (79 CS, 76 MACS, 77 controls) using an LC-MS/MS steroid panel. Individual and comparative diagnostic performance were assessed by receiver operating characteristic (ROC) analysis (AUROC, sensitivity, specificity); optimal cut-offs were determined by Youden’s index. We compared pre- versus post-DST metrics and examined subgroup (adrenal CS vs. pituitary CS) patterns.

RESULTS

Post-DST profiling materially improved discrimination of overt CS. The six key analytes—cortisol (F), cortisone (E), 11-deoxycortisol (11-DF), 11β-hydroxytestosterone (11β-OHT), corticosterone (CORT), and 18-hydroxycorticosterone (18-OHF)—each showed strong diagnostic performance, with most AUROCs ≥ 0.90. A multivariable logistic model integrating these six post-DST markers achieved similarly high AUROCs (≥ 0.90) across all primary comparisons. However, discrimination against MACS was attenuated, and the panel did not reliably distinguish pituitary from adrenal etiologies.

CONCLUSIONS

LC-MS/MS-based multi-hormone analysis of post-DST serum substantially enhances DST diagnostic accuracy for overt CS compared with baseline measures. Multi-hormone dynamics mitigate single F assessment limitations, offering a novel approach for diagnostic optimization and subclassification.