Since both high and low levels of cortisol are associated with multiple symptoms, cortisol testing often provides the answers to complicated health situations, which has led patient to multiple physicians without success. Successful diagnosis and treatment of the underlying problem improves patient symptoms, and cortisol testing provides an objective measurement of response to treatment. Salivary cortisol is preferred to serum measurements as a reliable indicator of adrenal status because it represents the free, bioavailable hormone levels, excluding the cortisol-binding globulin (CBG)-bound hormone that circulates in the blood but does not pass into saliva. The convenience of saliva collection and the avoidance of an anticipatory rise in cortisol levels caused by stress of venipuncture has been an advantage of salivary testing.
Estrogens (estrone, estradiol, estriol), progesterone, testosterone, DHEA-S and cortisol are routinely measured by saliva. Why saliva? Steroid hormones in the bloodstream are mostly (95-99%) bound to carrier proteins (hormone-binding globulins or albumins), and in this form they are unavailable to target tissues. Only the unbound fraction freely diffuses in the tissues, including the salivary gland. Hormone levels in saliva therefore represent the quantity of the hormone that is currently available to target tissues and is actively exerting specific effects on the body. Because of this, salivary hormone levels often relate to specific symptoms of hormone excesses of deficiencies. The rationale for and clinical utility of saliva testing is well documented. There is a good correlation between salivary hormone levels and dosages of hormones given exogenously. Saliva testing is therefore a good option for monitoring hormone therapy and adjusting dosages if necessary.