Interpretation of the discrepancy observed between plasma free and salivary testosterone levels in man.

The differences observed between plasma free and saliva testosterone levels do not result from methodological artefacts. We postulate that androgens metabolism in salivary glands modulates saliva testosterone levels both in men and women. In women, the "excess" of saliva testosterone (compared to the calculated free testosterone concentration), could be due to conversion of androstenedione in the salivary glands. The rate of this transformation is exaggerated in hirsute patients resulting in a significantly higher excess of saliva testosterone. In men, on the contrary, a "deficit" in saliva testosterone is observed suggesting testosterone transformation in salivary glands. This deficit is more marked in impotent men and appears to be reversed by testosterone administration. Saliva testosterone levels do not merely reflect plasma free hormone concentrations but also afford potentially useful information on androgens metabolism.