Comparison of Salivary Free Cortisol vs Serum Cortisol for the Assessment of the Hypothalamic-Pituitary-Axis (HPA)

Rupinder Kaur, Biochemistry

R Kaur, DM Kennedy and A Proudler

Cortisol is a hormone secreted by the adrenal glands. Measurement is important for diagnosis of adrenocorticotrophic dysfunction and therapeutic monitoring. This study will involve measurement of salivary cortisol by 3 different methods; LC-MSMS, automated immunoassay (Roche E170) and a highly sensitive ELISA specific for salivary cortisol.  Total Cortisol will be measured in serum using the Roche (E170).

The aim is to determine whether measurement of salivary cortisol could be an alternative to serum.   Collection of saliva has advantages e.g. it is less stressful than blood collection for anxious patients.  Salivary cortisol is unaffected by cortisol binding Globulin (CBG) and therefore alterations in CBG that might affect serum total Cortisol may be avoided.   Cortisol levels vary throughout the day so a single serum sample is of limited value.  Salivary cortisol analysis, may help avoid repeated invasive blood sampling.

Subjects will be recruited in the following groups; those undergoing a Short Synacthen Test, patients being monitored for adequacy of replacement, patients with Cyclical Cushing€™s syndrome and healthy volunteers

All will be asked to provide a saliva sample at the same time as serum cortisol is measured.  Comparison studies will then be performed to determine how well the measurement of salivary cortisol correlates with serum cortisol.