Evaluation of the overnight dexamethasone suppression test in a large cohort of patients with incidentally discovered adrenal nodules

Hassan Ibrahim; Faheem Muhammad; Sue Parsons; Lisa Yang; Sue Oddy; James MacFarlane; Andrew Powlson; Mark Gurnell; Ruth Casey

doi:10.1530/endoabs.109.P288

P288

Prev Next

Section Contents Cite

Endocrine Abstracts (2025) 109 P288 | DOI: 10.1530/endoabs.109.P288

SFEBES2025 Poster Presentations Late Breaking (68 abstracts)

Evaluation of the overnight dexamethasone suppression test in a large cohort of patients with incidentally discovered adrenal nodules

Hassan Ibrahim ¹ , Faheem Muhammad ¹ , Sue Parsons ¹ , Lisa Yang ¹ , Sue Oddy ¹ , James MacFarlane ² , Andrew Powlson ² , Mark Gurnell ^1,2 & Ruth Casey ¹

Author affiliations

¹Cambridge University Hospital NHS Foundation Trust, Cambridge, United Kingdom. ²Wellcome - MRC Institute of Metabolic Science, University of Cambridge, and NIHR Cambridge Biomedical Research Centre, Addenbrooke’s Hospital, Cambridge, United Kingdom

Introduction: Incidentally discovered adrenal nodules (AN) are detected in 1–7% of abdominal imaging studies. The 2023 ESE guidelines recommend the 1-mg overnight dexamethasone suppression test (ODST) for screening autonomous cortisol secretion (ACS). Previous studies suggest 20-50% of AN patients will fail an ODST which, in the absence of clinical evidence of Cushing’s syndrome (CS), is termed mild autonomous cortisol secretion (MACS). Herein, we report findings from a large cohort of patients with AN.

Methods: 512 patients (239 males, 273 females) referred between 2019 and 2023 were included. Patients with a positive ODST (cortisol ≥50 nmol/l) had dexamethasone level measured on the same sample to rule out false positives (defined as dexamethasone ≤3.7nmol/l). Patients with abnormal ODST and dexamethasone levels >3.7nmol/l were investigated for additional evidence of ACS defined as at least two of the following: elevated 24-hour urinary free cortisol, elevated late-night salivary cortisol, 9AM plasma ACTH <10pg/mL, suppressed DHEAS level.

Results: Of the 512 patients, 57 were excluded due to incomplete data, leaving 455. ODST was normal in 292 (64%) and abnormal in 163 (36%). Among the latter, 149 had adequate dexamethasone levels; 53/149 were not recommended for further investigations by the specialist adrenal MDT. Of the remaining 96 patients: 73/96 had no other clinical or biochemical evidence of ACS; 23/96 findings suggest ACS, including 3 with overt CS. Median cortisol was 88nmol/L in patients with additional positive biochemistry versus 78nmol/L in the abnormal ODST-only group (P=0.18).

Conclusion: Failed ODST occurred in 163 patients, with 14 false positives identified through dexamethasone measurement. Persistent biochemical evidence of ACS was identified in 23/96 patients, including 3 with overt CS. This study highlights the need to consider new biomarkers to identify MACS detection and stratify those at highest cardiovascular risk, while considering the economic and clinical burden of MACS screening.