Endocrine Abstracts

Background: Adrenal masses discovered incidentally during imaging studies (adrenal incidentalomas – AIs) are common and prompt investigations to exclude secretory lesions and malignancy. Uncertainty exists over the best management strategy of AI.

Objective: To monitor the current practice against the local protocol and existing guidelines; to identify the biochemical and imaging outcomes in a single centre cohort.

Methods: Retrospective review of medical records, biochemistry and imaging of all 125 patients referred to our centre between 2005 and 2009 with an AI.

Results: Eighty-two percent of the AIs were unilateral, average diameter on imaging was 20.4 mm. Eighty-seven percent of the patients had at least one repeat scan done, with a 17 months mean interval between the first and the last scan. 5.5% of AIs increased ≥5 mm in size on follow up, 7.8% decreased ≥5 mm, while 86.7% remained unchanged.

Following our local protocol and including only patients who completed all the investigations (82%), 67% patients were diagnosed with non secretory benign adenomas, 2% primary hyperaldosteronism, 2% phaeochromocytoma, 1% adrenal metastasis and 5% with other diagnosis. 24 patients (23%) failed to suppress on a low dose or overnight dexamethasone suppression test using a cut-off of 50 nmol/l; of those 4 were diagnosed with adrenal Cushing’s, 5 had false positive results. None of the remaining 15 patients had clinical features of Cushing’s syndrome and all but one had normal 24 h urinary free cortisol excretion. Finally, seven patients with at least two abnormal tests of the HPA axis were diagnosed with mild cortisol secretion. The use of a higher cut-off for post dexamethasone cortisol (83 nmol/l) would exclude four of these patients, while the recommended by the NIH consensus cut-off (138 nmol/l) would exclude all these patients but one.

Conclusion: Eleven percent of the AIs in our cohort were functional. Altering the post dexamethasone cortisol cut-off in accordance to published guidelines radically changed the performance of the suppression test in our cohort.