Quantitative determination of cortisol and cortisone from saliva by LC-MS/MS. Non-invasive assessment of adrenal function and HPA axis activity.
This method provides non-invasive measurement of salivary cortisol and cortisone for evaluation of adrenal function, circadian rhythm assessment, and diagnosis of Cushing's syndrome and adrenal insufficiency.
Clinical indications include:
| Analyte / Group | Components | Clinical Significance |
|---|---|---|
| Cortisol | Hydrocortisone | Primary glucocorticoid; regulates metabolism, immune response, and stress adaptation |
| Cortisone | 11-Dehydrocortisol | Inactive metabolite of cortisol; reflects local tissue cortisol inactivation by 11β-HSD2 |
The cortisol:cortisone ratio provides additional information about 11β-hydroxysteroid dehydrogenase (11β-HSD) enzyme activity.
Cortisol is the primary glucocorticoid hormone produced by the adrenal cortex, regulated by the hypothalamic-pituitary-adrenal (HPA) axis. It follows a pronounced circadian rhythm, peaking in the early morning and reaching its nadir around midnight.
Low late-night salivary cortisol helps exclude Cushing's syndrome
Cortisol follows a predictable diurnal pattern
Saliva collection avoids venepuncture stress artefacts
Salivary cortisol measurement offers a significant advantage over serum cortisol: saliva collection is non-invasive and stress-free, avoiding the cortisol elevation that venepuncture itself can cause. Salivary cortisol reflects the free (unbound) fraction of circulating cortisol, which is the biologically active form.
Late-night salivary cortisol has become a first-line screening test for Cushing's syndrome, as the loss of normal circadian nadir is one of the earliest biochemical abnormalities in this condition.
Both analytes are measured simultaneously by isotope-dilution LC-MS/MS, providing superior specificity compared to immunoassay methods. LC-MS/MS eliminates cross-reactivity with synthetic corticosteroids and other steroid metabolites that can cause false results in immunoassays.
Saliva samples are collected using a Salivette device at specified times (typically morning and late-night). The non-invasive collection method enables home sampling and is particularly valuable for paediatric patients and circadian rhythm studies.
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