CORTISOL, LC/MS, SALIVA, 4 SAMPLES

Salivary cortisol level, particularly late-night salivary cortisol (LNSC) level, is useful in screening for endogenous Cushing syndrome. Two or more positive results of LNSC tests may be used to confirm Cushing syndrome. LNSC measurement may also be used to monitor for recurrence of Cushing disease.

Normally, the secretion of cortisol has a circadian rhythm. Patients with Cushing syndrome often lose the late-night circadian nadir (= low point). Therefore, an elevated LNSC level may provide initial evidence for Cushing syndrome. Two or more positive results of LNSC tests may establish the diagnosis of Cushing syndrome if non-neoplastic hypercortisolism (pseudo-Cushing syndrome) is excluded. Because saliva is convenient to collect, LNSC testing is especially useful for individuals who need to provide multiple specimens over time for the evaluation of cyclic Cushing syndrome.

Annual LNSC testing is recommended to monitor for the recurrence of Cushing disease after pituitary surgery. LNSC testing may also be used in assessing treatment outcomes in patients receiving medical therapy for Cushing disease.

Non-neoplastic hypercortisolism caused by obesity, psychiatric disorders, alcohol use disorder, and polycystic ovary syndrome may increase LNSC levels. LNSC testing should not be used to screen for Cushing syndrome in individuals without normal day and night cycles. LNSC testing has low sensitivity in patients with adrenal tumors.

Other tests, such as urinary free cortisol and dexamethasone suppression test, may also be used to screen for Cushing syndrome. 

The results of this test should be interpreted in the context of pertinent clinical and family history and physical examination findings.