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

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

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

Prospective pharmacodynamic studies in clinical research facilities.

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.

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

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.

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.