Measurement of cortisol in the saliva is an alternative way of measuring the hormone, the monitoring of which is used to distinguish between primary and secondary adrenal insufficiency and for the differential diagnosis of Cushing's syndrome.
In addition, the measurement of cortisol in the saliva is used to study the disorders of the daily (circadian) secretion rhythm and to diagnose conditions such as adrenal stress or adrenal exhaustion.
Cortisol or hydrocortisone is the major glucocorticoid hormone produced in the adrenal cortex. Cortisol is actively involved in the regulation of calcium absorption, maintenance of blood pressure, it has anti-inflammatory actions, is involved in the regulation of gluconeogenesis, gastric acid, and pepsin secretion, and regulates immune function. Cortisol production shows a daily (circadian) rhythm. Its levels peak early in the morning and fall to their lowest levels at night. Cortisol levels rise regardless of circadian rhythm in response to stress. Elevated cortisol production is associated with Cushing's syndrome and adrenal tumors, while decreased cortisol production is associated with adrenal insufficiency (eg Addison's disease) and adrenocorticotropic hormone (ACTH) deficiency.
In the blood, only 1 to 15% of cortisol is in its unbound or biologically active form. The remaining cortisol binds to serum proteins. Free serum cortisol enters saliva through certain intracellular mechanisms while most of the cortisol in saliva remains unbound to proteins.
Salivary cortisol levels are not affected by salivary flow rate or salivary enzymes. Many studies report very high levels of correlation between serum and salivary cortisol measurements, indicating that salivary cortisol levels reliably assess cortisol levels in the body.
Measurements of hormones in saliva are an excellent choice, because the collection of the sample is non-invasive and easy, without the possible complications and inconvenience of blood sampling, while ensuring the sensitivity and accuracy of the measurements.