Endocrine Abstracts

Objective: The diagnosis of Cushing’s syndrome may be challenging, especially in cases of patients with chronic kidney disease (CKD).

Aim: The assessment of late night salivary cortisol concentration, serum and salivary concentration in overnight dexamethasone suppression test in patients with CKD stage III–V and a control group.

Patients and methods: 37 patients mean age 66±12 (M=13) with CKD stage III–V according to KDIGO and 28 controls mean age 45.3±15 years (M=6) were enrolled to the study. Patients were recruited in the nephrology clinic during their routine control visits. Serum and salivary cortisol were measured by Roche ECLIA cortisol test (Cobas E411). Two samples of late night salivary cortisol (LNSC) from each subject were obtained from home. 1 mg dexamethasone suppression test (DST) was done in patients and controls with serum and saliva measurement at 0800 h. Serum creatinine assessment was done no longer than 1 week prior to cortisol measurement. GFR was obtained from the Cockcroft−Gault calculator.

Results: The mean GFR in patients was 33.89 ml/min (8.4–54) while in controls 125 ml/min (73–230) (P<0.0001). The mean serum DST cortisol in patients was 2.62 μg/dl (0.46–7.42). In 19 (51.4%) patients serum DST cortisol was >1.8 μg/dl. In all controls serum DST cortisol was <1.8 μg/dl (mean, min–max 0.70, 0.36–1.48). The mean DST salivary cortisol in patients was 0.88 μg/dl (0.11–0.88) while in controls 0.18 μg/dl (0.02–0.69) μg/dl. Although there was a significant difference between controls’ and patients’ salivary cortisol concentration in DST (P=0.01), all but one patient’s salivary measurement were within control ranges. The mean LNSC in patients was 0.26 μg/dl (0.10–0.65) while in controls 0.29 μg/dl (0.04–0.80), P=0.4. All patients’ LNSC measurements were within control ranges. In the patients’ group the negative correlation between GFR and DST serum cortisol was detected, r=−0.6, P=0.001 (the higher cortisol the lower GFR).

Conclusion: LNSC may be helpful in excluding Cushing’s syndrome in patients with CKD.