Endocrine Abstracts

A 46-year-old gentleman presented with a history of general lethargy, weight gain, limb weakness, easy bruising and severe back ache. Examination showed central obesity, proximal myopathy, with marked thinning and extensive bruising of the skin. His blood pressure and glycemic control were suboptimal and resistant to treatment. Routine blood tests including a chest X-ray were normal. An overnight dexamethasone suppression test showed failed serum cortisol suppression (749 nmol/l) along with a markedly elevated 24 h urinary cortisol (3590 nmol/l) confirming a diagnosis of Cushing’s syndrome. The patient’s ACTH levels were grossly elevated (230 ng/l) and there was a suggestion of a suspicious 4 mm lesion on pituitary imaging. However in view of the short clinical history, high ACTH levels and equivocal radiology coupled with the fact that 10% of normal population harbour a pituitary incidentaloma, we proceeded to inferior petrosal sinus sampling (IPSS). This failed to demonstrate a central/peripheral ACTH gradient either basally or post-CRH. A CT scan of the thorax and abdomen raised the possibility of a mass in the pancreatic head. Octreotide scintigraphy with SPECT/CT acquisition confirmed a pancreatic tumour as the source of ectopic ACTH. The patient was initiated on metyrapone before a pylorus preserving pancreatic duodenectomy. The histology was typical of a neuroendocrine tumour of the pancreas. A postoperative dexamethasone suppression test along with a 24 h urinary free cortisol were normal. The patient is currently off all his antidiabetic medications along with a reduction in his anti-hypertensives.

Conclusions: Our case illustrates the value of IPSS in the investigation of ACTH-driven Cushing’s syndrome, particularly where pituitary radiology and clinical history are not typical for Cushing’s disease.

The case also highlights the importance of following a stepwise approach to the diagnostic work-up of patients with Cushing’s syndrome, including the use of appropriately timed cross-sectional and nuclear imaging modalities.