Simultaneous measurement of cortisol and cortisone in human saliva using liquid chromatography-tandem mass spectrometry: application in basal and stimulated conditions.
Immunoassays 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.
Perogamvros
Ilias
I
Department of Endocrinology, The Christie, Manchester, UK. ilias.perogamvros@nhs.net
Owen
Laura J
LJ
Newell-Price
John
J
Ray
David W
DW
Trainer
Peter J
PJ
Keevil
Brian G
BG
D002853:Chromatography, Liquid / Q000379:methods*; D003348:Cortisone / Q000032:analysis*; D006801:Humans; D006854:Hydrocortisone / Q000032:analysis*; D015203:Reproducibility of Results; D012463:Saliva / Q000737:chemistry*; D053719:Tandem Mass Spectrometry / Q000379:methods*
D003348:Cortisone; D006854:Hydrocortisone