ACTA ENDOCRINOLOGICA (BUC)

Introduction. Diagnosing Cushing Syndrome (CS) remains challenging due to its diverse symptoms and the complexity of its subtypes. This study aimed to optimize diagnostic cut-off values for differentiating CS subtypes using the 1 mg dexamethasone suppression test (DST) in a cohort of 237 patients. Materials and Methods. Retrospective data from patients diagnosed with non-functional adrenal adenomas (NFA), mild autonomous cortisol secretion (MACS), adrenal CS, and pituitary CS at the Dokuz Eylül University Endocrinology and Metabolism Clinic (2005–2016) were analyzed. Sensitivity and specificity of morning cortisol levels after DST were evaluated using receiver operating characteristic (ROC) curve analysis. Results. The analysis identified optimal morning cortisol cut-off levels: 2.14 μg/dL (59.04 nmol/L) for MACS, 2.3 μg/dL (63.4 nmol/L) for adrenal CS, and 2.33 μg/dL (64.28 nmol/L) for pituitary CS. Conclusion. These optimized thresholds demonstrated high sensitivity and specificity, significantly improving diagnostic precision over the conventional threshold of 1.8 μg/dL (50 nmol/L). The findings underscore the importance of tailored cut-off values to address subtype-specific diagnostic challenges, reducing delays and mitigating long-term complications. Personalized diagnostic approaches, incorporating patient demographics and disease-specific characteristics, are essential for enhancing diagnostic accuracy and facilitating timely interventions.