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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