ANNALS EXPRESS: Measuring cortisol in serum, urine and saliva – are our assays good enough?

El-Farhan, Nadia, Rees, Dafydd Aled ORCID: https://orcid.org/0000-0002-1165-9092 and Evans, Carol 2017. ANNALS EXPRESS: Measuring cortisol in serum, urine and saliva – are our assays good enough? Annals of Clinical Biochemistry 54 (3) , pp. 308-322. 10.1177/0004563216687335

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Abstract

Cortisol is a steroid hormone produced in response to stress. It is essential for maintaining health and well-being; and leads to significant morbidity when deficient or present in excess. It is lipophillic and is transported bound to cortisol-binding globulin (CBG) and albumin; a small fraction (~10%) of total serum cortisol is unbound and biologically active. Serum cortisol assays measure total cortisol and their results can be misleading in patients with altered serum protein concentrations. Automated immunoassays are used to measure cortisol but lack specificity and show significant interassay differences. Liquid chromatography – tandem mass spectrometry (LC-MS/MS) offers improved specificity and sensitivity; however cortisol cut-offs used in the short Synacthen and Dexamethasone suppression tests are yet to be validated for these assays. Urine free cortisol is used to screen for Cushing’s syndrome. Unbound cortisol is excreted unchanged in the urine and 24-hour urine free cortisol correlates well with mean serum free cortisol in conditions of cortisol excess. Urine free cortisol is measured predominantly by immunoassay or LC-MS/MS. Salivary cortisol also reflects changes in unbound serum cortisol and offers a reliable alternative to measuring free cortisol in serum. LC-MS/MS is the method of choice for measuring salivary cortisol; however, its use is limited by the lack of a single, validated reference range and poorly standardised assays. This review examines the methods available for measuring cortisol in serum, urine and saliva, explores cortisol in disease and considers the difficulties of measuring cortisol in acutely unwell patients and in neonates.

Item Type:	Article
Date Type:	Publication
Status:	Published
Schools:	Medicine Neuroscience and Mental Health Research Institute (NMHRI)
Subjects:	R Medicine > R Medicine (General)
Publisher:	SAGE Publications
ISSN:	0004-5632
Date of Acceptance:	12 December 2016
Last Modified:	02 Nov 2022 10:15
URI:	https://orca.cardiff.ac.uk/id/eprint/97964

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