Value of the Serum Dexamethasone Determination for the Diagnosis of Mild Autonomous Cortisol Secretion
Authors' conclusion
Up to 4% of the patients with MACS diagnosis based on a DST > 1.8 µg/dl do not achieve enough dexamethasone levels to suppress the hypothalamic pituitary adrenal axis, suggesting that the positive results in the DST were not related with autonomous cortisol secretion.
Study context
- Population
- Consecutive patients with adrenal incidentalomas (AIs) undergoing simultaneous serum dexamethasone (LC-MS/MS) and cortisol testing after the 1 mg DST
- Participants
- 140 patients
- Exposure
- Mild autonomous cortisol secretion (MACS) vs NFAI
- MACSn = 89
- NFAIsn = 51reference
- Outcome
- Dexamethasone bioavailability in the 1 mg DST (serum dexamethasone levels)
Methodological detailsprospective, consecutive patients
- Prospective
- Consecutive patients
Main finding
As reported in the abstract
Did not achieve proper serum dexamethasone levels (3.3 nmol/L threshold) during DST
Patients not achieving proper serum dexamethasone levels
3.6%
n = 5
Correlation between age and serum dexamethasone levels
r = 0.191
p = 0.024
Observational data: associations, not effects.
Further findings
Clinical and hormonal characteristics, MACS vs NFAIs
- MACS had higher late-night salivary cortisol and cortisol post-DST, lower DHEAS and ACTH than NFAIs
- MACS were older, with higher prevalence of hypertension, diabetes, and bilateral and larger adrenal tumors than NFAIs
Original publication
Value of the Serum Dexamethasone Determination for the Diagnosis of Mild Autonomous Cortisol Secretion. Clin Endocrinol (Oxf). Published 26 November 2025. doi:10.
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