Dexamethasone Suppression Test
North Devon District Hospital (Mon-Fri)
Serum (Gold Top)
Target Turnaround Time
1 working day
Investigation of Cushing’s syndrome or Hyperadrenalism – excess cortisol production.
Dexamethasone suppresses cortisol – a raised result is likely due to increased cortisol or ACTH production
1mg dose of dexamethasone (oral) given between 21:00 and 23:00hr (15ug/kg bodyweight in children).
Blood sample taken for analysis between 08:00 and 10:00 the following morning.
Cortisol reported. If a cortisol result is suppressed (<50nmol/L), a diagnosis of Cushing’s is unlikely.
If further confirmation is required, suggest 24-hour urine cortisol analysis. Sample collection containers and patient guidance are available.
Special Requirements & Notes
Indicate Dexamethasone Suppression Test is being undertaken on the order/form – laboratory comments relating to the analysis will be appended. If patients are on anticonvulsants, consider increasing the dose of dexamethasone as metabolism of the dexamethasone may be induced.