Impaired accuracy of the dexamethasone suppression test after bariatric surgery: implications for post-surgical cortisol interpretation.

This article investigates the impact of bariatric surgery (BS) on the 1 mg dexamethasone suppression test (DST), a diagnostic tool for assessing autonomous cortisol secretion. In a prospective longitudinal study of 38 patients, cortisol levels after DST were found to be higher two years post-BS compared to pre-surgery, with some patients showing cortisol levels above the standard suppression threshold despite no evidence of autonomous cortisol secretion. The study also demonstrated that plasma dexamethasone concentrations were significantly lower in post-BS patients compared to non-operated individuals with obesity and healthy controls, with BS and sex hormone–binding globulin (SHBG) levels identified as independent predictors of dexamethasone levels. These findings suggest altered dexamethasone metabolism or absorption after BS, which may lead to false-positive DST results, highlighting the importance of measuring plasma dexamethasone to improve DST interpretation in this population. Further research is recommended to validate these results and clarify the underlying mechanisms affecting DST reliability post-BS.