There is now sufficient evidence to show that standard serum (blood) testing protocols cannot quantify low concentrations of hormones in a reliable way. In general, blood measurements can only give the total steroid hormone concentration, whereas saliva testing measures the important free, bioavailable, hormone level.
At present most steroid hormone testing is conducted using the traditional method, i.e., by sampling and analysing blood – an invasive and costly procedure. Research has shown that, for most purposes involving otherwise healthy individuals, this method has limited application. Here’s why: Steroid hormones present in the blood are either completely “bound” to their specific binding globulins, or “free”. The bound component is biologically inactive and is considered to be a kind of hormone storage. Only less than 5% of the total hormones present are “free” or “bioavailable” and these are responsible for hormone activity in the body.
In serum (blood) or plasma testing, the steroid measurement represents the level of the total hormone, including the “bound” component. This total concentration at best gives only an approximate indication of the bioavailable hormone present in cases of completely healthy and normal patients. The Endocrine Society has published an official position statement*, stating that reliable measurements in serum testing either need an additional extraction step, or need to be completed using chromatographic methods, such as tandem MS or GCMS (super sophisticated and expensive equipment). This casts doubt on the validity of blood testing for free, bioavailable hormones.
Saliva testing for steroid hormones is now known to be the most reliable and convenient method for measuring the hormone activity in endocrine disorders and in checking hormonal balance. The sampling is non-invasive and can be done anytime, anywhere. Provided the proper testing procedure is observed, hormones tested reliably include: DHEA-S, cortisol, progesterone, estradiol, testosterone.