Endocrine Abstracts

Case History: 69 years old gentleman was referred to endocrinology for investigation of a benign appearing left incidental adrenal adenoma (1cm) after being investigated for abdominal pain. He had a past medical history of an abdominal aortic aneurysm (AAA), type 2 diabetes mellitus and hypertension.

Investigations: Initial endocrine investigations revealed normal 24h urinary free cortisol levels (twice), metanephrines and ARR. His overnight dexamethasone suppression test was abnormal (370 nmol/l – NR <50). The vascular surgeons were keen to undertake endovascular repair of his AAA. There were no stigmata of Cushing’s syndrome and together with unconvincing biochemical results, surgery was undertaken. His low dose dexamethasone suppression test failed to suppress his cortisol (135 nmol/l) with a baseline ACTH of 52.3 ng/l (NR 1.6 – 63.3). Moreover, his midnight cortisol was elevated (107 nmol/l). A pituitary MRI scan demonstrated a 4mm microadenoma. His repeated urinary free cortisol levels were abnormal (128 and 187 nmol/24h – NR 1-124). The patient declined pituitary surgery, and was commenced on Metyrapone titrating up to 1.5g BD. 11 months later, he agreed to have surgery. IPSS then confirmed Cushing’s Disease: left petrosal ACTH sampling showed a peak concentration of 1,203 ng/l and the right petrosal one was 1,165 ng/l (NR 1.6 – 63.3). The ratio favoured left sided hypersecretion. A repeat pituitary MRI scan, 24 months after initial scan, showed that the lesion had increased in size and had proteinaceous content. He is scheduled for explorative surgery.

Conclusion: We present a diagnostically challenging case of Cushing’s Disease, referred initially as adrenal incidentaloma. He had no clinical features of hypercortisolaemia and with unconvincing biochemistry, he underwent vascular surgery that was deemed necessary. Subsequent investigations confirmed pituitary source rather than ectopic or adrenal. Pituitary surgery has now been scheduled.