Saliva cortisol measurement: simple and reliable assessment of the glucocorticoid replacement therapy in Addison's disease

No ideal parameter is available for assessment of the glucocorticoid replacement therapy in Addison's disease. Serum cortisol day-curves can be used to monitor the therapy, but this technique is cumbersome and expensive. We evaluated the potential for saliva cortisol measurement in this setting. We found excellent correlation between serum and saliva cortisol after oral intake of cortisone acetate (no. 7) or iv administration of hydrocortisone (no. 4) (Pearson's R=0.83-0.98, p<0.002). A morning dose of 12.5 mg cortisone acetate yielded wide interindividual variations in cortisol levels in saliva. Saliva cortisol measurements were successfully adopted to evaluate and adjust doses in outpatients. We conclude that cortisol measurement in saliva is practical and reliable, and is preferable to serum cortisol measurement in the assessment of the glucocorticoid replacement therapy. Our results confirm that only a minority of patients require more than 12.5 mg of cortisone acetate (equivalent to 10 mg hydrocortisone) in the morning to have sufficient cortisol levels during the first part of the day.