Cortisol

Sample type: Serum

Test name: Cortisol a.k.a. dexamethasone suppression test

Condition / Indication: Addisons / Cushings

Special precautions & notes: Indications - suspicion of adrenal insufficiency. For diagnosis a short synacthen test is advised. For a short synacthen test, please ensure that a short synacthen test (rather than 3 separate cortisols) is requested. Multiple labels will be printed for the time points required.

Reference range: 8-10 am cortisol > 350 nmol/l usually considered to exclude Addisons unless on oestrogens or systemically unwell. A short synacthen test may be required to exclude Addisons: a stimulated cortisol (at either 30 or 60 minutes) ≥450 nmol/L excludes adrenal insufficiency, and in pregnant ladies, or those taking OCP, a higher threshold of 600 nmol/L applies. For investigation of Cushings, see document below to aid test selection.

Container: Serum (Gold top)

Ideal volume (mL): 5 mL

Referred outside NBT for analysis? No

Discipline: Clinical Biochemistry

Section: Automated Laboratory

Turnaround time: 1 day