Salivary cortisol: a better measure of adrenal cortical function than serum cortisol

SUMMARY Salivary cortisol concentration was found to be directly proportional to the serum un-bound cortisol concentration both in normal men and women and in women with elevated cortisol-binding globulin (CBG). The correlation was excellent in dynamic tests of adrenal function (dexamethasone suppression, ACTH stimulation), in normals and patients with adrenal insufficiency, in tests of circadian variation and randomly collected samples. Women in the third trimester of normal pregnancy exhibited elevated salivary cortisol throughout the day. The relationship between salivary and serum total cortisol concentration was markedly non-linear with a more rapid increase in salivary concentration once the serum CBG was saturated. The rate of equilibrium of cortisol between blood and saliva was very fast, being much less than 5 minutes. These data, combined with a simple, stress-free, non-invasive collection procedure, lead us to suggest that salivary cortisol is a more appropriate measure for the clinical assessment of adrenocortical function than is serum cortisol. Materials and methods SUBJECTS Circadian variation The circadian rhythm of salivary cortisol was examined in seven female and seven male healthy adults (age range 24-32 years). Each subject collected a saliva sample every hour for one day throughout their normal waking hours. On another day the same groups provided matched serum and saliva samples at 0900 and 1700. The circadian rhythm of salivary cortisol in the third trimester of normal pregnancy was examined in 13 sets of samples from 10 women (age range 22-35 years) with uncomplicated pregnancies who delivered healthy single babies at 38-42 weeks' gestation. dexamethasone suppression, adrenocorticotrophin (ACTH) stimulation, and circadian variation; (3) examined the circadian variation of salivary cortisol in women in the third trimester of normal pregnancy; and (4) examined the rate of appearance of cortisol in saliva. Dexamethasone suppressionlAC'I'H stimulation Six male and five female healthy young adults received dexamethasone (1 mg orally) at 2200, and samples of serum and saliva were obtained at 0900 the next day