Time-integrated measurement of corticosteroids in saliva by Oral Diffusion Sink technology

Saliva, as a medium for assessing adrenocortical function in humans, has many advantages and a few distinct disadvantages. Interpretation of measurements of saliva cortisol is complicated by the contamination of saliva by steroid-binding proteins from blood plasma, enzyme ac-tivity in the salivary gland that converts cortisol to corti-sone, and the amplification in saliva of the episodic fluctuations in systemic cortisol concentrations. We de-scribe a new measurement technology that rejects arti-facts from contamination of saliva by plasma protein, provides for measurement of both cortisol and cortisone, and integrates episodic fluctuations in concentration over a period of hours. This oral diffusionsink technology may greatly enhance the reliable interpretation of cortico-steroid concentrations measured in saliva. AddItIonal Keyphrasee: coilisol ‘ cortisone. variation, source of Saliva has many advantages as a medium for assess-ing adrenocortical function in humans. Not only is saliva much more convenient to collect than blood or urine, but also concentrations of the corticosteroid hor-mones in saliva generally reflect the concentration of the free fraction of corticosteroids in blood plasma (1,2). This is important because most endocrine effects are thought to be exerted by the free concentration, rather than by the much larger concentration reversibly bound to the corticosteroid-binding globulin in plasma, and because the free concentration is related in a distinctly nonlinear way to the total corticosteroid concentration (3). To the degree that corticosteroid concentrations in saliva mirror those of the free concentration in plasma, they provide more direct information about the avail-ability of corticosteroids to tissue. The relation of saliva cortisol to free cortisol in plasma does not depend on the saliva flow rate (1,4,5), and the change in saliva concentrations with systemic changes is prompt (6). However, problems in the interpretation of corticosteroid concentrations in saliva exist, related to the following three factors: #{149}in practice, saliva is frequently contaminated to some extent with plasma proteins, including corticoste-roid-binding globulin and its reversibly bound cortico