Salivary cortisol - General Information

Cortisol is a lipophilic steroid with low molecular weight (MW ~362 Dalton). Following ACTH binding to membrane receptors on cells of the adrenal cortex, cortisol is synthesized and released into the blood stream. Up to 95% of the secreted cortisol will be bound to large proteins (CBG, albumin) and carried throughout the body in the blood. Since the vast majority of cortisol actions rely on binding to its cytosolic mineralocorticoid and glucocorticoid receptors, only the small fraction of unbound, i.e., free cortisol is thought to be biologically active. Due to its low molecular weight and lipophilic nature, unbound cortisol enters cells by passive diffusion which makes it feasible to measure the free cortisol fraction in all bodily fluids. While the assessment of cortisol in sweat or tears is only of theoretical importance and urinary cortisol of decreasing interest, salivary cortisol has become an invaluable tool for both basic scientists and clinicans. A number of significant advantages over the assessment of cortisol in blood has resulted in a steadily increasing interest in salivary cortisol.

Cortisol
Cortisol

FAQs (frequently asked questions) about salivary cortisol

Q: Does the concentration of cortisol in saliva acurately reflect the level in blood?

Q: Does the concentration of cortisol in saliva acurately reflect the level in blood?

A: Yes, when compared to the amount of unbound cortisol in serum or plasma samples. A number of studies have revealed correlations between the two specimen of r > 0.90. However, the correlation between the total cortisol levels in blood and salivary cortisol is usually weaker due to different amounts of CBG found in blood (e.g., high levels of CBG due to oral contraceptive use results in high total cortisol levels; free cortisol levels are usually unaltered in states of increased CBG).

 

 

Q: Does the salivary cortisol levels depend on saliva flow rate?

Q: Does the salivary cortisol levels depend on saliva flow rate?

A: No. Studies looking at salivary cortisol levels obtained under minimal and maximal flow rate clearly showed that the cortisol levels in saliva do not depend on flow rate.

 

 

Q: How can I obtain a saliva sample for cortisol analysis?

The Salivette
The Salivette

Q: How can I obtain a saliva sample for cortisol analysis?

A: The easiest way for sampling saliva is to use a device called the "Salivette". The Salivette is manufactured and sold by Sarstedt (http://www.sarstedt.com). Subjects should be instructed to gently chew on the cotton roll to stimulate saliva flow rate. With this it usually takes less than a minute to obtain a saliva sample of 0.5-1 ml volume.

Important:
DO NOT USE THE CITRIC ACID STIMULATED SALIVETTES (green caps)!! Saliva samples obtained with these devices have a low pH which interfers with most immunoassays known. It produces false high cortisol levels. We recommend to use the Salivettes with the blue caps.

 

 

Q: Which medications or food ingredients will interfer with salivary cortisol?

Q: Which medications or food ingredients will interfer with salivary cortisol?

A: The level of salivary cortisol is influenced by drugs such as prednisone, dexamethasone and other steroids administered orally or i.v. While prednisone usually crossreacts with the antiserum used for assaying cortisol (leading to false high values), dexamethasone will significantly suppress the HPA axis (resulting in low cortisol levels). Furthermore, if the subjects deliver saliva samples with a low pH (e.g., following stimulation of saliva flow by crystals of vitamin C, consumption of fruit juices immediately before sampling etc.) most immunoassay will produce false high cortisol levels.

 

 

Q: Do I have to store the saliva samples in the refrigerator or freezer immediately?

Q: Do I have to store the saliva samples in the refrigerator or freezer immediately?

A: Although there is data suggesting that cortisol may be stable at room temperature for a period of 2 weeks, we recommend that samples are stored at 4 °C or below as soon as possible after sampling. Sampling devices like Salivettes may begin to mold within 4-7 days at room temperature, producing a very badly smelling sample. While this may not affect cortisol levels, it sure affects the mood of the technicians assaying the samples! In the long term, saliva samples should be stored at -20 °C (or -80 °C, if available)

 

 

Q: Do I have to use dry ice if I send my samples to the laboratory?

Q: Do I have to use dry ice if I send my samples to the laboratory?

A: We recommend to use dry ice or to send the samples with cooling packs in a polystyrene box. This will prevent the samples from molding. If this is not possible, express shipping is a good alternative.

 

 

Q: Does repeated freezing and thawing of the saliva samples affect the cortisol levels?

Q: Does repeated freezing and thawing of the saliva samples affect the cortisol levels?

A: No.

 

 

Q: How or where can I have my saliva samples assayed for cortisol?

Q: How or where can I have my saliva samples assayed for cortisol?

A: There are different options available today. First, several diagnostic companies now offer commercial assay kits for cortisol determination in saliva. Three reliable assays are sold by

These assays appear to give correct values with acceptable sample volumes required. If you do not have a lab or the time to run the assays yourself, you can also send your samples to a lab which provides assay service. Besides our own lab in Dresden, there are other research labs as well as commercial labs which offer custom assays.

 

 

Q: How can I find out how accurate/reliable a lab is?

Q: How can I find out how accurate/reliable a lab is?

A: All laboratories should comply with the principles of good laboratory practice (GLP) especially regarding quality assurance. This involves the use of internal and external controls, duplicate or multiple determinations and evaluation of intra- and inter-assay coefficients of variation (CVs) for all analysis.

 

 

Q: What are the assay costs for a salivary cortisol determination?

Q: What are the assay costs for a salivary cortisol determination?

A: If you decide to purchase a kit and do the assays in your own lab, the price differs widely and depends on the conditions you obtain from the manufacturer. As a rule of thumb, expect to pay 3-5 USD per duplicate analysis (including standards and controls) for the reagents. If you send your samples to a lab which offers assays service, expect to pay between 2.50 - 15 USD for the same analysis.

 

 

Instructions on labelling and shipping samples

download instructions (126 kb)

Order Form Saliva

Order Form Saliva

 

 

(More detailed technical information can be obtained from our scientific papers under "Publications". Most papers are available as PDF documents)

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