Preferred Sample Type
Suitable Specimen Types
- Serum
- Li Hep Plasma
Sample Processing in Laboratory
Usual
Sample Preparation
Centrifuge
Turnaround Time
1 daySample Stability
Store at 4 ºC for up to five days. For longer periods store at -20 ºC.
Cortisol
General Information
Cortisol is the most significant glucocorticosteroid and is essential for the maintenance of several body functions. Like other glucocorticosteroids it is synthesised in the zona fasciculata of the cortex of the Adrenal gland. Cortisol is secreted in response to adrenocorticotrophic hormone (ACTH) which is released from the anterior pituitary gland. Cortisol is bound to cortisol-binding globulin and albumin with only the free (unbound) fraction being biologically active
Blood and urine tests for cortisol may be used to help diagnose Cushing’s syndrome and Addison’s disease, two serious disorders affecting the production of cortisol by the adrenal gland. Cushing's syndrome is caused prolonged exposure to elevated levels of either endogenous glucocorticoids or exogenous glucocorticoids, while Addison's disease is caused by damage to the adrenal, and is associated with too little cortisol. However, a single random cortisol measurement is of limited diagnostic value. Therefore, if cortisol concentrations are abnormal, additional testing may be required to confirm the diagnosis and decide on treatment.
These may include a dexamethasone suppression test or 24 hour urinary cortisol in the diagnosis of Cushing's syndrome, or a short synacthen test (SST) for the diagnosis of Addison's disease/adrenal insufficiency.
Patient Preparation
The collection time should be noted on the request form.
Samples from patients receiving high biotin doses (i.e. >5 mg/day) should be taken at least 8 hours post dose.
Pregnancy, contraceptives and oestrogen therapy give rise to elevated cortisol concentrations.
Samples from patients treated with prednisolone, methyl-prednisolone or prednisone may give falsely elevated concentrations of cortisol. Therefore, if your patient is taking these mediciations please order a Prednisone Test.
Notes
Samples should be clot-free and free of red cells or other particulate matter. The presence of fibrin may cause erroneous results.
Reference Range
Before 10 am: 101.2 - 535.7 nmol/L,
After 5 pm: 79 - 477.8 nmol/L,
(Source: Abbott Diagnostics)
Specifications
- EQA Scheme?: Yes
-
EQA Status:
NEQAS and WEQAS