Endocrine Abstracts

Summary: Physiological replacement of glucocorticoids in hypocortisolemic patients remains a challenge. We assessed the use of salivary cortisol and total serum cortisol profile with CBG measurement in monitoring glucocorticoid replacement in hypoadrenal patients in routine clinical practice.

Methods: Serum and salivary cortisol concentrations were measured in 60 hypoadrenal patients previously documented to have cortisol deficiency on provocative testing. Assays were performed at different time points together with baseline corticosteroid binding globulin (CBG) according to patients’ routine hydrocortisone replacement therapy which was usually thrice daily. Free cortisol index was calculated as total serum cortisol/cortisol binding globulin (CBG) ratio.

Results: The CBG concentration was higher in women than in men and higher in women on estrogen replacement than those who were not. There was a wide interindividual variability in the concentrations of cortisol in both saliva and serum after oral administration of hydrocortisone. Salivary cortisol showed no gender differences There was a strong correlation between baseline serum and salivary cortisol before the first dose of HC was taken (r=0.70; P<0.001) except in those who had high (10 nmol/l) salivary cortisols at baseline. After the first dose of HC, all patients showed a modest correlation between salivary and blood cortisol values.

Conclusion: Cortisol day profiles are widely used to monitor replacement therapy. However, they do not take account of individual variation of cortisol metabolism or tissue sensitivity and are only useful in patients who take hydrocortisone or cortisone acetate. The results indicate that measurement of CBG and calculation of free cortisol index offers few benefits over assays of total serum cortisol concentrations. Salivary cortisol measures may be useful in patients taking lower doses of hydrocortisone as they are non-invasive and may avoid the need for patients to attend hospital.