Cortisol in saliva
Why this test?
For the diagnosis of Itsenko-Cushing's syndrome or disease and Addison's disease - serious endocrinological diseases.
To evaluate the effectiveness of the treatment of the syndrome or Itsenko-Cushing's disease and Addison's disease.
When is it prescribed?
In case of suspicion of Itsenko-Cushing syndrome (symptoms: increased blood pressure, obesity, muscle dystrophy, stretch marks on the abdomen) or Addison's disease (symptoms: weakness, fatigue, low blood pressure, skin pigmentation).
In cases of ineffectiveness of attempts to normalize elevated blood pressure.
With growth retardation and excess weight in children.
In the case of volume neoplasms of the adrenal glands (incidentalomas) accidentally detected on ultrasound;
When conducting a dexamethasone test (prescribed for depression, consists of two determinations of cortisol concentration before and one day after taking dexamethasone);
With long-term therapy with glucocorticosteroids.
At certain intervals, when the patient is being treated for the syndrome/Itsenko-Cushing's disease or Addison's disease.
Cortisol is a hormone that is produced in the cortex of the adrenal glands. It protects the body from stress, regulates the level of blood pressure, participates in the exchange of proteins, fats and carbohydrates. Cortisol is found in blood, urine and saliva. Analysis of cortisol in saliva is performed to assess the concentration of its free, biologically active form. Cortisol in saliva is the most accurate and convenient marker of an acute response to stress, and this indicator can also be used for screening and diagnosing pathologies of the hypothalamic-pituitary-adrenal system.
The release of cortisol is regulated by adrenocorticotropic hormone (ACTH), which is produced in the pituitary gland. The concentrations of ACTH and cortisol in the blood are regulated by the feedback method. A decrease in the concentration of cortisol increases the production of ACTH, as a result of which the production of this hormone is stimulated until it returns to normal. An increase in the concentration of cortisol in the blood, on the contrary, leads to a decrease in the production of ACTH.
Therefore, the concentration of cortisol in the blood can change with an increase or decrease in the secretion of both cortisol itself in the adrenal glands and ACTH in the pituitary gland, for example, in the case of a pituitary tumor that secretes ACTH.
All these functions are performed only by the biologically active, free fraction of cortisol. In the blood, this hormone circulates mainly in protein-bound form, free cortisol is from 1 to 15% of total serum cortisol. Only molecules with a small molecular weight can penetrate through the membranes of the salivary glands, it is too high for molecules of cortisol bound to transport proteins to overcome this barrier. Therefore, only free, active cortisol penetrates from the blood to the saliva.
The concentration of free cortisol in saliva depends on the same factors as its concentration in the blood:
- cortisol-producing activity of the cortex of the adrenal glands;
- ACTH-producing activity of the pituitary gland;
- time of day (normally early in the morning the concentration of cortisol in saliva is maximum, in the afternoon it decreases by an average of 54%, at 11-24 hours it reaches a minimum, it decreases by 89% compared to the morning);
- stress is the main factor that causes a sharp increase in the level of cortisol in all biological fluids.
The concentration of digestive enzymes in it and the intensity of saliva secretion do not affect the cortisol level in saliva. The change in the concentration of cortisol in blood and saliva occurs synchronously, studies confirm that cortisol in saliva increases 1 minute after the increase in blood, and the peak concentration in blood and saliva is reached with an interval of 2-3 minutes. At the same time, the concentration of free cortisol in saliva is 10-35% lower than in blood plasma, this is due to its partial conversion to cortisone when passing through the salivary glands.
Salivary cortisol analysis is a non-invasive study, the simplicity and painlessness of collecting biological material makes this method the most convenient in cases where it is necessary to repeatedly re-estimate the concentration of free cortisol.