Quantitative Analysis of Salivary Cortisol Using LC-MS/MS

Area of Science:

• Endocrinology
• Clinical Chemistry
• Analytical Chemistry

Background:

• Cortisol, a key glucocorticoid, is vital for human metabolism.
• Midnight salivary cortisol correlates with serum free cortisol, aiding Cushing's syndrome diagnosis.

Purpose of the Study:

• To describe a validated liquid chromatography-tandem mass spectrometry (LC-MS/MS) method for quantifying midnight salivary cortisol.
• To ensure accurate and specific measurement of cortisol in saliva for diagnostic purposes.

Main Methods:

• Saliva samples undergo centrifugation, dilution with buffer, and addition of deuterated internal standard (D4-cortisol).
• Samples are analyzed using reverse-phase separation on a C18 column via LC-MS/MS.
• Quantification relies on comparing sample responses to known calibrator concentrations.

Main Results:

• The LC-MS/MS method provides specific and accurate quantification of salivary cortisol.
• Multiple reaction monitoring ensures analytical specificity by using unique fragment ions.

Conclusions:

• This LC-MS/MS method is suitable for the precise measurement of midnight salivary cortisol.
• The validated assay supports the clinical utility of salivary cortisol testing for diagnosing endocrine disorders like Cushing's syndrome.