Is the 1mg-dexamethasone suppression test a precise marker of glucocorticoid excess and cardiometabolic risk in patients with adrenal incidentalomas?

AIM: To analyze if the 1mg-dexamethasone suppression test (DST) is a reliable marker of glucocorticoid excess and cardiometabolic risk in patients with adrenal incidentalomas (AIs). METHODS: Cross-sectional study of patients with nonfunctioning adrenal incidentalomas (NFAIs, defined by cortisol post-DST ≤ 1.8 µg/dL) and patients with autonomous cortisol secretion (ACS, defined by cortisol post-DST > 1.8 µg/Dl). The urinary steroid profile (USP) was determined by gas chromatography coupled to mass spectrometry. Both groups were matched by sex, age and body mass index. RESULTS: Forty-nine patients with AIs (25 with ACS and 24 with NFAI) were included. As a whole, AIs showed a high excretion of ß-cortolone, tetrahydro-11-deoxycortisol (THS), α-cortolone, α-cortol, tetrahydrocortisol (THF) and tetrahydrocortisone (THE). A positive yet modest correlation between post-DST cortisol and total excretion of glucocorticoid metabolites (r = 0.401, P = 0.004) was observed, with the stronger being observed with total THS (r = 0.548, P < 0.001) and THF (r = 0.441, P = 0.002). Some of the metabolites that were elevated in patients with AIs, were higher in patients with ACS-related comorbidities than in those without comorbidities. Post-DST cortisol showed a fair diagnostic accuracy for the prediction of ACS-related comorbidities (AUC 0.767 [95% CI 0.634-0.882]). However, post-DST diagnostic accuracy improved when combined with urinary cortisone, α-cortol, THS and serum DHEAS (0.853 [0.712‒0.954]). CONCLUSION: The DST has a positive, but modest, correlation with urinary glucocorticoid excretion. Similarly, the diagnostic accuracy of the DST for the prediction of ACS-related comorbidities is only fair, but it may be improved if combined with the results of the USP and serum DHEAS. SIGNIFICANCE STATEMENT: This is the first study aimed to evaluate if 1mg-dexamethasone suppression test (DST) is a reliable marker of glucocorticoid excess and cardiometabolic risk in patients with adrenal incidentalomas (AIs) and if urinary steroid profile was measured by GS-MS could improve such a prediction. We found a positive yet modest correlation between post-DST cortisol and total excretion of glucocorticoid metabolites, with the stronger being observed with total tetrahydro-11-deoxycortisol (THS) and tetrahydrocortisol. Post-DST cortisol showed a fair diagnostic accuracy for the prediction of ACS-related comorbidities (AUC 0.767). However, post-DST diagnostic accuracy improved when combined with urinary cortisone, α-cortol, THS and serum DHEAS (0.853).