Endocrine Abstracts

Context: Late-night salivary cortisol is a recommended screening method for Cushing’s syndrome. Liquorice intake may lead to falsely elevated salivary cortisol as glycyrrhizic acid inhibits the 11β-hydroxysteroid dehydrogenase type 2 induced conversion of cortisol to cortisone in the salivary glands. Furthermore, sample contamination by blood from the oral mucosa may also cause falsely elevated salivary cortisol levels. Salivary cortisone has been suggested to more closely reflect free plasma cortisol and is less likely to be affected by these preanalytical errors.

Objective: To determine if (i) liquorice consumption significantly increases late-night salivary cortisol levels, and if so, what dose is required for this to happen and how long wash-out period is required for salivary cortisol levels to normalize; (ii) what level of blood contamination lead to significantly increased salivary cortisol levels.

Design: Thirty healthy volunteers abstained from liquorice for four weeks prior to the study. Participants were randomized to a low, medium or high dose of liquorice, corresponding to a daily glycyrrhizic acid dose of 1.5, 3.0 or 6.0 mg/kg body weight. Saliva samples were collected during five days of baseline sampling, one week of daily liquorice consumption and four weeks of wash-out. Another sixteen healthy volunteers collected both saliva and blood samples, which were mixed to achieve a graded blood contamination of the saliva. Salivary cortisol and cortisone were analyzed with LC-MS/MS. Blood contamination was quantified using Cobas Hemolysis index (Roche Diagnostics) and by visual examination on a 7-point scale.

Results: Significant increases of salivary cortisol levels were observed during the seven days of liquorice intake in the medium and high dose groups (median increase 66% and 137%, respectively). The salivary cortisol levels returned to baseline four days after liquorice withdrawal in both groups. Salivary cortisol increased significantly by a 0.5% blood contamination. Visual grading corresponded very well to hemolysis index. Salivary cortisone levels were not affected by liquorice consumption or blood contamination.

Conclusion: Liquorice intake equivalent to a glycyrrhizic acid dose of 3–6 mg/kg body weight, corresponding to a daily intake of 100 g liquorice candy for a 70 kg person, causes a significant increase in late-night salivary cortisol levels. This effect weans off after four days. Saliva samples with a blood contamination of 0.5% leads to significantly increased salivary cortisol levels. Visual screening is sufficient to exclude significantly blood contaminated samples. Salivary cortisone levels are independent of both these preanalytical errors.