Cholesterol (CHOL, total cholesterol)
Melbourne Health Shared Pathology Service
|Cortisol (CORT) |
|Specimens |Blood 5 ml, lithium-heparin or serum tube for cortisol blood levels. |
| |Urine, 24 h collection in a plain container for excretion studies. |
| |Saliva, collected in the pledget supplied for salivary levels. |
|Test availability |Assayed daily in blood; weekly in saliva and urine. |
|Reference intervals | |
| |Time, h |
|Adult, |0800-0900 |
|male & female |1500-1600 |
| |2300 |
| |unit |
| | |
| |Blood |
| |150 - 650 |
| |120 - 400 |
| |* |
| |nmol/L |
| | |
| |Saliva |
| | |
| |* |
| |< 6.2 |
| |nmol/L |
| | |
| | |
| |* no interval stated for this time |
| | |
| |Urinary excretion: 100 – 379 nmol/d |
|Uncertainty of measurement: CVa: RMH, blood, 5.7% at 558 nmol/L; saliva, 27% at 14.9 nmol/L; |
|urine, 6.2% at 179 nmol/L . |
|Clinical applications and interpretation |
|Blood assays |
|Blood cortisol levels assess adrenocortical function in the response limb of a suppression or stimulation test. |
|See the separate page for each dynamic test for advice on that procedure and the interpretation of results. Scroll down to find |
|them. |
| |
|The random assay of cortisol in blood is only indicated as an initial test to exclude pituitary insufficiency or in the confirmation |
|of Addisonian crisis. |
| |
|Salivary assays |
|Salivary cortisol, which can be collected “at home” using the supplied collecting pledget, is particularly useful in establishing |
|late evening trough levels; it similarly permits morning samples to be collected without having to attend a clinic. Midnight salivary|
|cortisol collections are not used in night shift workers or patients with irregular sleeping hours. |
|The MHSPS laboratory uses the Salivette( pledget; no other device is accepted. Scroll down to find details of this test. |
| |
|The cortisol assayed in saliva is solely the free, (non protein-bound), hormone. |
| |
|Urine assays |
|Excretion of cortisol in urine is used to demonstrate increased hormone secretion. The 24 h collection serves to integrate hormone |
|clearance over the circadian cycle. |
|Increases may occur with primary or with secondary adrenocortical hyperfunction, but may also be seen where the patient is obese, |
|stressed or depressed, and with excess alcohol consumption. |
|Urine cortisol levels are not used to evaluate adrenal hypofunction; the Synacthen stimulation test is appropriate there. |
|Links | |
| References |RCPA Manual of Test Use, Version 4. RCPA, Sydney, 2004. Reference |
| |intervals are derived from assay manufacturers, and have been confirmed by in-house studies. |
|This page last reviewed and verified: 6 October 2010 by C Chiang. |
Melbourne Health Shared Pathology Service
|Cortisol (CORT) |
|Clinical applications: How to use the Salivette. |
| |
|The MHSPS laboratory uses the Sarstedt Salivette( pledget (O/N 51.1534) to permit patients to collect saliva for the assay of |
|cortisol; no other device is accepted. |
| |
|For midnight salivary cortisol in the evaluation of Cushing’s Syndrome, one Salivette is used at 11 pm (2300 h). Salivettes are |
|composed of an outer, conical shaped, tube with a plastic insert that contains a cotton swab or pledget. |
| |
|Collection procedure |
|Plan ahead … |
|Do not drink any citrus juices, e.g., orange juice, just prior to the collection. |
|Fifteen (15) minutes before the collection rinse the mouth thoroughly with plain tap water. |
|After the mouth rinsing, do not eat or drink anything else until the saliva collection is completed. |
| |
|The collection … |
|Remove the plastic lid from the Salivette. |
|Remove the cotton swab from the Salivette with your fingers. |
| |
|Place the swab in the mouth and leave it there for 3 minutes; you may move the swab around in your mouth but must not chew on it; |
|thinking of lemon juice, just thinking, usually induces salivation. |
|After 3 minutes spit the swab directly from your mouth into the Salivette, without handling it, and then put the supplied lid on. |
| |
|Label the Salivette with your name, hospital record number, date of birth, the date of the day when you did the collection, the time |
|of collection. |
|Store the capped Salivettes in the kitchen refrigerator at about 4o C. |
| |
| |
|Finally, transport specimen to the laboratory the next morning. |
This page last reviewed and verified : 6 October 2010 by C Chiang.
Melbourne Health Shared Pathology Service
|Cortisol (CORT) |
|Dexamethasone suppression test, overnight |
|(the 1mg dexamethasone suppression test) |
|Clinical application |
|This is the initial investigation when Cushing’s syndrome is suspected. |
|Dexamethasone, a cortisol analogue, is administered to assess the negative feedback inhibition of ACTH secretion by the anterior |
|pituitary gland. |
| |
|Dexamethasone is approximately 25 times as potent as cortisol. |
|Usual total daily secretion of cortisol by the adrenal glands in the adult is approximately 7 to 10 mg. |
|Requirements |
|Dexamethasone, two 500 μg tablets, to make a 1 mg dose. |
|No special patient preparation is needed; the test can be initiated “at home” provided blood samples can be drawn as required by the|
|protocol. |
|Protocol |
| Day 1, 2200 – 2400 h: swallow dexamethasone, all the tablets at once. |
|Day 2, 0800 – 0900 h: response cortisol, collect blood 5 ml, lithium-heparin or serum tube. |
|Interpretation |
|The day 2,morning cortisol should suppress,to less than 50 nmol/L. (Ref:J Clin Endocrinol Metab. 2008 May;93(5):1526-40). |
|If day 2 cortisol is: |
|< 50nmol/L, sensitivity 95%, specificity 80% |
|< 140nmol/L, sensitivity 85%, specificity 95% |
| |
|Failure to suppress indicates that cortisol production is not responsive to normal feedback inhibitory mechanisms. |
|Failure to suppress |
|… occurs with Cushing’s syndrome, Cushing’s disease, exogenous steroid use and ectopic ACTH secretion |
|… but may, however, also be seen in patients with endogenous depression, stress, or obesity, and with chronic excessive|
|alcohol consumption … and|
|as an effect of certain drugs which caused rapid metabolism of the oral dexamethasone dosee.g., phenytoin. |
|Concealed failure to take the dexamethasone and abnormalities of dexamethasone absorption or metabolism should also be considered if |
|there is a failure to suppress that is clinically incongruous. |
| References |RCPA Manual of Test Use, Version 4. RCPA, Sydney, 2004. Ismail |
| |AAA. Biochemical Investigations in Endocrinology. Methods and Interpretations. Academic Press, |
| |London, 1981. |
|This page last reviewed and verified: 6 October 2010 by C Chiang. |
|END OF PROTOCOL |
Melbourne Health Shared Pathology Service
|Cortisol (CORT) |
|Dexamethasone suppression test (high dose suppression test) |
|Clinical application |
|This is the test used to determine the source of ACTH dependent Cushing’s syndrome. |
|The test may be done according to the prolonged schedule described or as a high-dose, overnight test. |
|Requirements |
|Dexamethasone, 500 μg tablets. |
|Protocol |
|Dosing: the prolonged schedule |
|Days 1 & 2, baseline assessment: no steroid medication. |
|Days 3 & 4, low dose medication: dexamethasone, 500 μg, qid. |
|Days 5 & 6, high dose medication: dexamethasone, 2 mg, qid. |
|Day 7, final assessment day: no steroid medication. |
| |
|Sampling, every day for the 7 days |
|Urine, 24 h collection into plain container for cortisol excretion. |
|Blood, 0900 h, collect 5 ml, lithium-heparin or serum tube for cortisol. |
|Blood, 0900 h, collect 10 ml, EDTA tube, immediately onto ice, for ACTH. |
|Both blood samples must be sent to the laboratory immediately, each day. |
| |
|An alternative regime |
|Alternatively, 8 mg of dexamethasone can be given as a single dose late in the evening. |
|Interpretation of the cortisol response then moves immediately to the end of the schedule below and is done in conjunction with ACTH |
|assay results and other investigations as needed. |
|Interpretation |
|Cortisol results |
|Suppression is defined as a reduction of the morning cortisol level to ................
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