Measurement of Steroid Hormones in Saliva

For many years few methods were sensitive enough to measure steroid hormones in blood or saliva. For that reason many steroids were measured in urine. These measurements provided useful information to the clinician since they reflected the actual production rates in the body over a period of time. Urinary free cortisol and urinary free estradiol, estrone and testosterone were considered indicators of the respective blood levels.

Today urinary measurements of hormones are used less frequently. The main disadvantage of this method is the requirement of a 24 hour urine sample which many patients consider an inconvenience. Most hormones are now measured in serum or plasma using RIA or ELISA assays. These methods are reliable and sensitive and provide accurate results about the hormonal status of a patient. A major limitation of blood testing is that measurements represent total hormone levels, that is the sum of "free" (bioavailable) and "bound" hormones. Another disadvantage of this approach is the fluctuation and pulsatility of blood hormone levels. Multiple blood samples are often necessary to overcome this limitation.

Free Versus Bound Hormones
Hormones in the circulation occur in a "bound" and a "free" form. The majority (95 99%) of steroid hormones in the blood are bound to carrier proteins such as cortisol binding globulin (CBG), sex hormones binding globulin (SHBG) and albumin. In this bound form they are unavailable to target tissues. The remaining 1 5% of hormone concentration in blood represents the free or bioavailable hormone. The bioavailable fraction binds to the steroid receptors and elicits the biochemical effects. Thus, knowledge of free hormone is desirable in a number of clinical situations.

Despite the clinical usefulness, measurements of free hormone levels in blood are not routinely employed. The major drawbacks are the technical difficulties and the high cost of the assays.

Hormones in Saliva
The concept of measuring free hormone has been in scientific literature for a number of years with the documented clinical utility of urinary free cortisol. Other applications include the measurement of free and weakly bound testosterone in the clinical workup of the patient presenting with hirsutism.

Besides urine and blood, saliva is another diagnostic medium to measure steroid hormones. It is a natural ultrafiltrate of blood, and steroids not bound by carrier proteins freely diffuse into saliva. Since the concentration of carrier proteins in saliva is extremely low, measurements in saliva for the most part represent the free fraction of the hormone.

Over the past 20 years many studies have validated the use of saliva for hormone measurement such as testosterone, estradiol, estrone, progesterone, DHEA and cortisol. Unfortunately, the unavailability of commercial assays with extremely high sensitivities have slowed the introduction of these assays into the routine laboratory.

We have developed a series of sensitive assays which allow the analysis of steroid hormones in saliva. The tests have great accuracy are reliable and provide detailed information on the hormone status of a patient. The correlation between saliva and serum concentrations is greater than 90 percent.