Diagnostic performance of salivary cortisol in the diagnosis of Cushing's syndrome, adrenal incidentaloma and adrenal insufficiency.

Salivary cortisol has been recently suggested for studies on the hypothalamic-pituitary-adrenal (HPA) axis: lack of circadian rhythm is a marker of Cushing's syndrome (CS), and some authors report that low salivary cortisol levels may be a marker of adrenal insufficiency. The aim of our study was to define the role of salivary cortisol in specific diagnostic setting of HPA axis disease. SUBJECTS AND METHODS: We analyzed morning salivary cortisol (MSC) and late night salivary cortisol (LNSC) in 406 subjects: 52 Cushing's disease (CD), 13 ectopic-CS, 17 adrenal-CS, 27 CD in remission (mean follow-up of 66 ± 39 months), 45 adrenal incidentalomas, 73 patients assessed of CS and then ruled out for endogenous hypercortisolism, 75 patients with adrenal insufficiency and 104 healthy subjects. RESULTS: A LNSC value above 5.24 ng/mL differentiated CS from controls with high sensitivity (96.3%) and specificity (97.1%), we found higher LNSC in ectopic-CS than in CD. We found no difference in MSC and LNSC levels between CD in remission and healthy subjects. Both MSC and LNSC were higher in adrenal incidentaloma than in healthy controls. MSC below 2.65 ng/mL distinguished patients with adrenal insufficiency from controls with high sensitivity (97.1%) and specificity (93.3%). CONCLUSIONS: salivary cortisol is a useful tool to assess endogenous cortisol excess or adrenal insufficiency and to evaluate stable CD in remission