What health information can our saliva give us?
The majority of hormones (for example: cortisol, DHEA, progesterone, testosterone) in the blood exist in one of two forms: free (5%) or protein bound (95%). While 95% of the hormones in the body are protein bound, it is only the 5% free hormones that are biologically active.
In order for steroid hormones to be detected in serum i.e. in your typical blood draw, they must be bound to circulating proteins. In this bound state, they are unable to bind to receptors in our tissues which means that the hormones cannot carry out its intended effects (FYI: for hormones to carry out its intended purpose, it must be bound to a receptor. When the hormones are bound to circulating proteins, it means that they cannot bind to their target receptors). Therefore, hormones that are measured in serum or blood is considered inactive or non-bioavailable.
Saliva, on the other hand, measures the free, bioavailable hormone aka active levels in the body. Why is this?
When blood is filtered through the salivary glands, the bound hormone components are too large to pass through the cell membranes of the salivary glands. Only the unbound hormones pass through and into the saliva. What is measured in the saliva is considered the “free”, or bioavailable hormone, that which will be delivered to the receptors in the tissues of the body. Therefore, saliva is the method of choice when assessing functional hormone levels.
The discrepancy between free and protein bound hormones becomes especially important when monitoring topical, or transdermal, hormone therapy. Studies show that this method of delivery results in increased tissue hormone levels (thus measurable in saliva), but no parallel increase in serum levels. Therefore, serum testing cannot be used to monitor topical hormone therapy.
Saliva testing is proving to be a very reliable medium for measuring hormone levels. Hormone levels in saliva accurately represent the amount of hormone delivered to receptors in the body, unlike serum which represents hormone levels that may or may not be delivered to receptors of the body. Clinically, it is far more relevant to test the amount of hormones delivered to the tissue receptors as this is a reflection of the active hormone levels of the body.