what is a salivary cortisol
Late-Night Salivary Cortisol. Late-night salivary cortisol is one of the most sensitive diagnostic tests for Cushingâs syndrome. Elevated cortisol between 11:00 p.m. and midnight appears to be the earliest detectable abnormality in many patients with this disorder.hree diagnostic studies are currently recommended: late-night salivary cortisol, 24 hour urine free cortisol, low-dose dexamethasone suppression. If any of these tests is abnormal, a referral to an endocrinologist is strongly encouraged.