First-author, Natalia Genere, MD and co-authors had the findings of their cross-sectional study published in “The Journal of Clinical Endocrinology & Metabolism” on October 14. The publication is titled, “Interpretation of Abnormal Dexamethasone Suppression Test is Enhanced With Use of Synchronous Free Cortisol Assessment.”
Dexamethasone suppression test (DST) is a standard of care endocrine test for evaluation of adrenal masses and for patients suspected to have endogenous Cushing’s syndrome.
The study by Genere and collaborators intended to determine the normal range of free cortisol during the 1 mg DST. The study included volunteers without adrenal disorders and patients assessed for cortisol excess for clinical reasons.
Interpretation of DST is affected by the dexamethasone absorption and metabolism, and some studies report false-positives because of inadequate dexamethasone concentrations. Another source of false-positives is the difference in the proportion of cortisol bound to corticosteroid binding globulin affecting total cortisol concentrations.
An assessment of free cortisol after a dexamethasone suppression test could add value to the diagnostic workup of hypercortisolism, which can be plagued by false-positive results, according to data from the study.
Based on their findings, the authors suggested a sequential approach to dexamethasone suppression in clinical practice.
The authors stated, “We recommend a stepwise approach to enhance DST interpretation, with the addition of dexamethasone concentration and/or free cortisol in cases of abnormal post-DST total cortisol,” Bancos said. “We found dexamethasone concentrations are particularly helpful when post-DST total cortisol is at least 5 µg/dL and free cortisol is helpful in a patient with optimal dexamethasone concentrations and a post-DST total cortisol between 1.8 µg/dL and 5 µg/dL. We believe that DST with free cortisol is a useful addition to the repertoire of available testing for [mild autonomous cortisol secretion], and that its use reduces need for repetitive assessments and patient burden of care, especially in women treated with oral contraceptive therapy.”