Use of salivary cortisol and cortisone in the high- and low-dose synacthen test.

Context: Salivary cortisone reflects serum cortisol levels, is more sensitive than salivary cortisol at lower values of serum cortisol and is noninvasive.

Objective: To investigate the relationship between serum cortisol and salivary cortisol and cortisone following low- and high-dose synacthen.

Design And Setting: Prospective pharmacodynamic studies in clinical research facilities.

Participants And Intervention: Thirty-five dexamethasone-suppressed, healthy adult males underwent an intravenous synacthen test: N = 23 low-dose (1 mcg), N = 12 high-dose (250 mcg). Paired serum and salivary samples were taken at 15 sampling points over 120 minutes.

Main Outcome Measure: Serum cortisol and salivary cortisol and cortisone were analysed for correlations and by a mixed-effects model.

Results: At baseline, the correlation between serum cortisol and salivary cortisol was weak with many samples undetectable (r = .45, NS), but there was a strong correlation with salivary cortisone (r = .94, P < .001). Up to 50 minutes following synacthen, the correlation coefficient between serum cortisol and salivary cortisol and cortisone was <0.8, but both had a stronger correlation at 60 minutes (salivary cortisol r = .89, P < .001, salivary cortisone r = .85, P < .001). The relationship was examined excluding samples in the dynamic phase (baseline to 60 minutes). Salivary cortisol and cortisone showed a close relationship to serum cortisol. Salivary cortisone showed the stronger correlation: salivary cortisol r = .82, P < .001, salivary cortisone r = .96, P < .001.

Conclusion: Following synacthen, both salivary cortisol and cortisone reflect serum cortisol levels, but there is a lag in their rise up to 60 minutes. The results support further research for possible future use of a 60-minute salivary cortisone measurement during the synacthen test.