The study, done by researchers from Germany, was called “Salivary Cortisol as a Diagnostic Tool for Hyper- and Hypocortisolism: Improved Screening by an Automated Immunoassay.”
In this study, there were 40 patients with confirmed hypercortisolism. There were 12 who had Cushing’s disease, 2 with ectopic Cushing’s syndrome, and 26 with adrenal Cushing syndrome. These patients were compared to 115 healthy subjects and 45 control patients with adrenal masses (18 had non-functioning adenoma, 15 had pheochromocytoma, and 12 had aldosterone-producing adenoma).
Also, 63 patients with proven hypothalamic-pituitary disease were in the study; there were 54 with sellar masses and 9 with hormonal impairment.
Saliva sampling was performed at 11pm and 8am following low-dose dexamethasone suppression. The researchers used receiver operating characteristics (ROC) analysis to calculate the thresholds (with at least 95% sensitivity) for hypercortisolism. To define adrenal insufficiency, a peak serum cortisol level below 500 nmol/l during an insulin hypoglycemia test was used.
The researchers collected unstimulated saliva samples at 8am; ROC analysis was done to establish the lower and upper cutoffs with at least 95% specificity (for either adrenal insufficiency or adrenal sufficiency). A commercially-available ECLIA was used to perform the salivary cortisol measurements.
The study found that an 11pm salivary cortisol cutoff of 6.06 nmol/l (sensitivity 95%; specificity 92%; AUC 0.97) and a dexamethasone-suppressed salivary cortisol cutoff of 2.02 nmol/l (sensitibity 97%; specificity 86%; AUC 0.98) were calculated for diagnosing hypercortisolism.
In regards to the HPA axis, there was a lower cutoff of 3.21 nmol/l and an upper cutoff of 20.4 nmol/l that identified 12 out of 31 patients (39%) as having adrenal insufficiency; the same cutoffs identified 2 out of 32 patients (6%) as adrenal sufficient.
These newly-established thresholds give the practitioner an excellent tool for identifying both hypercortisolism and hypocortisolism by using an automated immunoassay. This will allow for a broader use of salivary cortisol as a routine diagnostic tool for hypercortisolism and hypocortisolism.