Differences between concentrations of salivary cortisol and cortisone and of free cortisol and cortisone in plasma during pregnancy and postpartum.

We measured cortisol and cortisone in plasma--both total and free--and in saliva during the course of pregnancy and postpartum. Antepartum and postpartum concentrations and morning and afternoon concentrations of both steroids were compared. The mean concentrations of cortisol and cortisone increased towards term and were significantly greater at the end of pregnancy than postpartum, except for free cortisol in plasma in the afternoon. The daily rhythm of both steroids was maintained throughout pregnancy and postpartum. The correlations between salivary and plasma free concentrations of cortisol and cortisone as well as of the sum of cortisol + cortisone were highly significant. The mean concentrations of cortisone in saliva accurately reflected both total and free concentrations in plasma. For cortisol, however, the change of the concentrations in saliva, was somewhat different from that in plasma. Moreover, the mass ratio of plasma free cortisol to salivary cortisol was about 2, whereas for cortisone the ratio was only about 0.5, probably owing to the conversion of cortisol to cortisone by 11 beta-hydroxysteroid dehydrogenase in the salivary gland. Furthermore, the passage of cortisol and cortisone from plasma to saliva should not be regarded as simple diffusion, because in the first half of pregnancy the sum of the concentrations of cortisol + cortisone in saliva significantly exceeded the sum of their free concentrations in plasma.