Simultaneous measurement of cortisol and cortisone in human saliva using liquid chromatography-tandem mass spectrometry: application in basal and stimulated conditions.
Owen, Laura J
Ray, David W
Trainer, Peter J
Keevil, Brian G
AffiliationDepartment of Endocrinology, The Christie, Manchester, UK. firstname.lastname@example.org
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AbstractImmunoassays used for the measurement of salivary cortisol are limited by variable interference from cortisone. Salivary cortisone is a consequence of the salivary glands expressing 11beta-hydroxysteroid dehydrogenase type 2 (11beta-HSD2) which converts cortisol to cortisone. We report a combined salivary cortisol and cortisone (SalF and SalE respectively) liquid chromatography-tandem mass spectrometry (LC-MS/MS) assay to address the cortisone cross-reactivity in cortisol immunoassays and as a tool to study 11beta-HSD2 activity. The method was linear up to 400 nmol/L for SalF and 200 nmol/L for SalE and the lower limits of quantitation were 0.39 nmol/L (SalF) and 0.78 nmol/L (SalE). No evidence of ion suppression was found and precision, accuracy and recovery were within internationally accepted limits. No interference was identified from 13 structurally related steroids. SalF, SalE and SalF/SalE were significantly greater in the morning than at bed-time and following stimulation of the adrenal glands. As serum cortisol increased, an exponential rise was observed in SalF and a linear increase in SalE which reached a plateau at higher SalF concentrations. We have developed a novel, robust LC-MS/MS assay for the combined measurement of SalF and SalE. Our results confirm the 11beta-HSD2 activity of the salivary glands resulting in high SalE concentrations and the enzyme saturation at high substrate concentrations. This method can be used as a simple, non-invasive and highly specific tool to assess the value of salivary cortisol as a surrogate for free serum cortisol and as a potential novel way to assess 11beta-HSD2 activity.
CitationSimultaneous measurement of cortisol and cortisone in human saliva using liquid chromatography-tandem mass spectrometry: application in basal and stimulated conditions. 2009, 877 (29):3771-5 J. Chromatogr. B Analyt. Technol. Biomed. Life Sci.
JournalJournal of Chromatography. B, Analytical Technologies in the Biomedical and Life Sciences