Plasma cortisol cut-off concentrations using the dexamethasone suppression test in patients with adrenal incidentalomas.
Assessment of cortisol secretion in patients with adrenal incidentalomas remains challenging. We evaluated the guideline-recommended cortisol cut-off value for cortisol suppression (50 nmol/L) following a 1 mg overnight dexamethasone suppression test (DST) against a control-derived threshold and compared patient classification using the two thresholds. Secondary objectives included assessing associations of pre-DST ACTH, post-DST dexamethasone, and comorbidities with post-DST cortisol.
In this cross-sectional study (NCT07350031), pre- and post-DST plasma samples from patients with adrenal incidentalomas (N = 108) and matched controls (N = 101) were prospectively collected, and cortisol was analysed using immunoassay (Elecsys®Cort II) and LC-MS/MS. Post-DST dexamethasone ≥3 nmol/L defined appropriate dexamethasone exposure. The 97.5th percentile of LC-MS/MS-measured post-DST cortisol in controls defined the control-derived threshold. Associations between pre-DST ACTH, post-DST dexamethasone, and post-DST cortisol were assessed. The performance of pre-DST ACTH for identifying post-DST cortisol >50 nmol/L was evaluated using receiver operating characteristic analysis. Logistic regression examined associations between post-DST cortisol and diabetes, dyslipidaemia, hypertension, and osteoporosis.
The 97.5th percentile of post-DST cortisol in controls was 66 nmol/L. The 50 nmol/L threshold corresponded to the 90th percentile of controls and classified 44% of patients as having hypercortisolism, compared with 26% using the control-derived threshold (66 nmol/L). Pre-DST ACTH showed poor discrimination for post-DST cortisol >50 nmol/L (AUC 0.69). Post-DST cortisol was not associated with dexamethasone concentrations or comorbidities.
The guideline-recommended post-DST cortisol threshold of 50 nmol/L may be too low, suggesting that higher thresholds warrant further evaluation.
In this cross-sectional study (NCT07350031), pre- and post-DST plasma samples from patients with adrenal incidentalomas (N = 108) and matched controls (N = 101) were prospectively collected, and cortisol was analysed using immunoassay (Elecsys®Cort II) and LC-MS/MS. Post-DST dexamethasone ≥3 nmol/L defined appropriate dexamethasone exposure. The 97.5th percentile of LC-MS/MS-measured post-DST cortisol in controls defined the control-derived threshold. Associations between pre-DST ACTH, post-DST dexamethasone, and post-DST cortisol were assessed. The performance of pre-DST ACTH for identifying post-DST cortisol >50 nmol/L was evaluated using receiver operating characteristic analysis. Logistic regression examined associations between post-DST cortisol and diabetes, dyslipidaemia, hypertension, and osteoporosis.
The 97.5th percentile of post-DST cortisol in controls was 66 nmol/L. The 50 nmol/L threshold corresponded to the 90th percentile of controls and classified 44% of patients as having hypercortisolism, compared with 26% using the control-derived threshold (66 nmol/L). Pre-DST ACTH showed poor discrimination for post-DST cortisol >50 nmol/L (AUC 0.69). Post-DST cortisol was not associated with dexamethasone concentrations or comorbidities.
The guideline-recommended post-DST cortisol threshold of 50 nmol/L may be too low, suggesting that higher thresholds warrant further evaluation.
Authors
Jørgensen Jørgensen, Borresen Borresen, Hilsted Hilsted, Christoffersen Christoffersen, Brødbæk Brødbæk, Ugleholdt Ugleholdt, Feltoft Feltoft, Skaanning Skaanning, Thorsby Thorsby, Rasmussen Rasmussen, Feldt-Rasmussen Feldt-Rasmussen, Klose Klose
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