Endocrine Abstracts

Background: Adrenal incidentalomas (AI) are being seen frequently in endocrine clinics due to increased cross-sectional imaging with a prevalence of 4% (7% in patients >70 years) of abdominal CT scans. The majority of these tumours are benign and non-functional, but identifying malignancy and functionality is important. Excess cortisol production is the commonest endocrinopathy associated with AI, with a reported prevalence of ~10%. The overnight 1 mg dexamethasone suppression test (ONDST) is one of the recommended tests for assessing glucocorticoid.

Aim: To evaluate the prevalence of excess cortisol production in a cohort of AI patients referred to our hospital.

Methods: Patients referred to our endocrine clinic from July 2016 till May 2018. All patients underwent ONDST with cortisol suppression to <50 nmol/l considered normal. We also measured the diurnal serum and salivary cortisol/cortisone levels and serum dexamethasone levels, as a surrogate for dexamethasone absorption.

Results: Twenty-five patients, 16 women (64%), with a median age of 55.48±7.99 years. 7 (28%) had hypertension, 7 (28%) had type 2 diabetes mellitus and 4 (16%) had both. A total of 16 (64%), failed to suppress to ONDST (cortisol ≥50). 15 (60%) had values of 51–130 nmol/l and 1 (4%) had a value >130 nmol/l. 4 (16%) patients had midnight salivary cortisol concentrations of ≥2.8 nmol/l. We are currently analysing the dexamethasone data and correlating them with the post dexamethasone cortisol data.

Conclusion: The prevalence of excess cortisol, based on the ONDST, is higher than previously reported. There is discordance between the results of the ONDST and the diurnal rhythm evaluation. The value of measuring dexamethasone levels in ONDST needs further evaluation.