Corticosteroids in plasma and saliva : the influence of oral contraceptive use and pregnancy

Cortisol in saliva is considered to be derived from the free, unbound fraction in plasma by simple diffusion through the salivary gland. Despite considerable conversion into cortisone in the salivary gland by the enzyme 11β-hydroxysteroid dehydrogenase, levels of cortisol in saliva form a good reflection of the free plasma fraction, which is considered to be the biologically active part. In the present study the relation between plasma free and salivary concentrations of cortisol and cortisone were investigated in women with regard to the influence of hormonal status. Similarly, progesterone was measured in plasma and saliva during pregnancy to demonstrate the relation between plasma free and salivary progesterone. In addition, the daily rhythm of cortisol and cortisone and the influence of hormonal status was investigated on the basis of salivary levels. Further, the effect of processing of salivary samples on the concentration found for several steroids was determined. It appeared that transport of corticosteroids from plasma to saliva is not a simple diffusion proces, but probably proceeds via specific binding proteins in the cell membrane at both the plasma side and the saliva side of the gland cells