Evaluation of the success of salivary cortisol in determining diagnostic value and diurnal rhythm as measured by immunoassay and tandem mass spectrometry methods in patients who needs to be excluded from hypercortisolemia

Nonfunctional adrenal adenomas and other rare masses constitute 75-80% of adrenal lesions, whereas 20-25% of them are functional adrenal adenomas that cause pheochromocytoma, androgen-producing tumor, primary hyperaldosteronism, Cushing's Syndrome (CS) or Subclinical Cushing Syndrome (SCS). 1 mg dexamethasone suppression test used for CS and SCS diagnosis. Even in same person, cortisol may show significant variability after 1 mg dexamethasone at different times. There are few studies on diagnostic value of salivary cortisol, taken at midnight and at certain hours of the day, in adrenal CS and SCS. In this study, we aimed to develop a method for measuring salivary cortisol by LC-MS/MS, to compare the developed method with ELISA and to evaluate the diagnostic value and its success for revealing diurnal rhythm. Comprehensive method validation studies were performed and saliva samples taken at 08.00, 16.00, 24.00 from CS (n=20), SCS (n=52) and non-functional adenoma (NFA) (n=49) patients were analyzed. Cortisol levels in samples taken at 24.00 had high sensitivity and specificity in CS and SCS. Salivary cortisol levels in samples taken at 16.00 and 24.00 were significantly higher with both method in CS group than SCS and NFA. Cortisol levels in SCS were significantly higher than NFA. Diurnal rhythm was high in CS, moderately high in SCS at noon and evening hours, reached the highest level in the morning the lowest level at midnight in NFA. LC-MS/MS method was sensitive and reliable for salivary cortisol measurement, and consistent with ELISA method. Salivary cortisol measurement by LC-MS/MS reflected diurnal rhythm.