Subclinical Cushings syndrome (SCs) is used to refer to an adrenal incidentaloma with subtle autonomous cortisol secretion and without typical signs and symptoms of hypercortisolism. Diagnostic criteria are uncertain and arbitrary. In this study we aimed to investigate the power of adenoma size as an independent predictor of SCs.
Dokuz Eylul University Adrenal Tumours Study Group database includes 596 patients by January 2016. Briefly, there are 332 subjects with non functioning adrenal adenomas and 141 subjects (adrenal Cushing Syndrome was excluded) with alterations in 1 mg dexamethasone suppression tests (1 mg DST). We stratified the individuals according to the 1 mg DST results. Group A (n=310, 1 mg DST <1.8 μg/dl), Group B (n=68, 1.8 <1 mg DST<3 μg/dl), Group C (n=46, 3<1 mg DST<5 μg/dl) and Group D (n=26, 1 mg DST > 5 μg/dl). Adenoma size showed a strong relation with 1 mg DST results. Median size was 20, 25, 33 and 31 mm in Group A to D, respectively. The ROC curve analysis showed that the cut-off of the adenoma diameter with the best diagnostic accuracy for detecting individuals with a non-suppressed 1 mg DST level (>3 μg/dl) was 25 mm (sensitivity, 80%; specificity, 74%; AUC: 0.808, P<0.001). We also evaluated prospective hormonal data in 110 individuals and demonstrated that 1 mg DST results were substantially stable among individuals.
The limitation of SCs screening to the individuals with larger adenomas would decrease medical costs and further time consuming procedures.