Late Night Salivary Cortisol in the Diagnosis of Neoplastic Hypercortisolism (including Cyclic Cushing's Syndrome)

Late night salivary cortisol (LNSC) is a mainstay in the diagnosis of neoplastic hypercortisolism (Cushing's syndrome) with a sensitivity and specificity of > 90% in patients with syndromic signs and symptoms. Intermittent hormonogenesis (day to day variation) is common in milder Cushing's disease whereas true cyclic Cushing's syndrome (weeks to months of tumor quiescence) is unusual. In both cases, LNSC is useful as a sensitive evaluative diagnostic tool, although its lower specificity may lead to false positive results in patients without Cushing's disease. Furthermore, intermittent hormonogenesis may lead to false negative LNSC results in patients with mild Cushing's disease. Finally, LNSC is useful as an approach to follow patients after pituitary surgery to detect a recurrence even many years after a full remission.