• The assay is fully automated, with less than 8 minutes time to first results, allowing you to efficiently provide accurate biologically active plasma free cortisol results
  • The assay calibrators are traceable to an isotope dilution-mass spectrometry (ID-MS), from the Reference Institute for Bioanalytics (www.rfb.bio)
  • The assay has excellent precision, functional sensitivity (0.02 µg/dL) and a wide assay measurable range (0.02-3.00µg/dL), giving you further confidence in the quality of assay results

The IDS-iSYS Salivary Cortisol assay is intended for the quantitative determination of cortisol in human saliva on the IDS-iSYS Multi-Discipline Automated System family. Results are to be used as an aid in the assessment of Cushing’s and other disorders of the hypothalamic pituitary adrenal axis.

Cortisol is a steroid hormone synthesised in the cortex of the adrenal gland. This glucocorticoid plays a role in the metabolism of carbohydrates, fat and protein, the maintenance of myocardial function, and the adaptation to stress1. Approximately 90% of cortisol in plasma or serum is protein bound to cortisol-binding-globulin (CBG). Measurement of unbound cortisol found in saliva is an accurate method to assess the biologically active free plasma cortisol2,3. CBG concentrations decrease with certain liver and kidney diseases, resulting in decreased serum cortisol concentrations. The unbound fraction, as in saliva, is said to remain constant4.

In healthy subjects, cortisol levels peak at 7–9 a.m., with levels falling for the rest of the day5. Patients with abnormal function of the adrenal gland lose normal circadian rhythm and have higher levels of cortisol at midnight6.

Measuring late night salivary cortisol is an easy and non-invasive means of diagnosing diseases of cortisol imbalance such as Cushing’s (CS). Salivary cortisol is most useful as the initial test when CS is suspected and for periodic patient monitoring after pituitary surgery for Cushing’s7,8.

  1. John J. Bray et al. Lecture notes on human physiology. Third Edition Published by Blackwell Science 1994.
  2. David W., The Immunoassay Handbook. Third Edition. D.Wild (Ed.) Published by Elsevier Ltd. 2005.
  3. Yaneva M., Mosnier-Pudar H., Dugue M-A., Grabar S., Fulla Y. and Bertagna X., ‘Midnight salivary cortisol for the initial diagnosis of Cushing’s and various causes’. J Clin Endocrinol Metab, 89(7), 2004, pp 3345-3351.
  4. Aardal, E. and Holm, A-C., ‘Cortisol in saliva – reference ranges and relation to cortisol in serum’. Eur J Clin Chem Clin Biochem, 33, 1995, 927-932.
  5. Rossi GP., Seccia TM. and Pessina AC., ‘Clinical use of laboratory tests for the identification of secondary forms of arterial hypertension’. Crit Rev Clin Sci, 44(1), 2007, pp 1-85.
  6. Nieman LK., Biller BMK., Findling JW., Newell-Price J., Savage MO., Stewart PM., and Montori VM., ‘The diagnosis of Cushing’s: an endocrine society clinical practice guideline’. J Clin Endocrinol Metab, 93, 2008, pp 1526-1540.
  7. Raff, H., ‘Cushing’s: diagnosis and surveillance using salivary cortisol’. Pituitary, 15, 2012, pp 64-70.
  8. Raff, H., ‘Update on late-night salivary cortisol for the diagnosis of Cushing’s: methodological considerations’. Endocrine, 44, 2013, pp 346-349.