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Salivary cortisone measurements correlate with serum cortisol, offer noninvasive alternative
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Salivary cortisone measurements strongly correlate with serum cortisol measurements and may serve as a noninvasive alternative to estimate serum cortisol and serum free cortisol, according to research in The Journal of Clinical Endocrinology & Metabolism.
In a prospective crossover study, Miguel Debono, MD, MRCP, PGDip, PhD, an NIHR clinical lecturer at the University of Sheffield, U.K. and colleagues analyzed data from 14 healthy men (mean age, 28 years; mean BMI, 25.3 kg/m²) who provided blood and saliva samples over three study periods. During three study periods, researchers measured serum and saliva cortisol and cortisone, serum albumin, cortisol binding globulin and free cortisol, and analyzed for rhythm parameters and correlations using linear mixed effects modeling. During study period 1, researchers analyzed 24-hour physiologic cortisol rhythm. During study periods 2 and 3, participants were given 20 mg oral hydrocortisone and IV hydrocortisone, respectively.
Miguel Debono
Researchers found that serum cortisol and cortisone measurements showed similar circadian rhythms with large peak-to-trough ratios for both cortisol (11.05 nmol/L; 95% CI, 6.57-66.77) and cortisone (6.16 nmol/L; 95% CI, 3.37-15.24). The mean peak-to-trough ratios for cortisol binding globulin and albumin were 1.12 mg/L (95% CI, 1.1-1.14) and 1.09 g/L (95% CI, 1.09-1.1), respectively.
Salivary cortisol was undetectable when serum cortisol was less than 74 nmol/L, whereas salivary cortisone was always detected. Due to contamination, salivary cortisol measurements taken after oral hydrocortisone produced unreliable results. However, salivary cortisone correlated strongly with serum cortisol under physiologic conditions (correlation coefficient p: 0.91; 95% CI, 0.89-0.93) and following intravenous or oral hydrocortisone (p: 0.91; 95% CI, 0.89-0.92).
A mixed effects model showed that in this population, 94% of the variation in salivary cortisone could be predicted from serum cortisol, according to researchers.
“Salivary cortisone has previously been shown to have a linear relationship to serum cortisol,” the researchers wrote. “We have now extended this observation by modeling the relationship in fine detail over 24 hours, confirming it exists under both physiological cortisol secretion and after the administration of hydrocortisone, and by defining the key parameters of salivary cortisone levels over 24 hours.”
“Some endocrinologists still carry out cortisol day curves as part of the management of patients on conventional hydrocortisone replacement,” Debono told Endocrine Today. “We have shown that salivary cortisone can be used as an alternative to measuring serum cortisol in these patients.” – by Regina Schaffer
Disclosure: Two of the study authors are directors of Diurnal Ltd; another author reports serving as a consultant to Diurnal Ltd.
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