Endocrine Abstracts

Case history: A 41-year-old female presenting with abdominal pain and melaena, was found to have a left adrenal incidentaloma on her abdominal CT. Her past medical history included polycystic ovaries, menstrual irregularity, fibromyalgia and gallstones. Medications on presentation were lansoprazole and dihydrocodeine only. On further questioning, she was experiencing hair loss, proximal muscle weakness, bruising and striae, weight changes and low mood.

Investigations: Under the endocrine team, she went on to have an adrenal MRI which confirmed an 11 mm benign adenoma. Additionally, she had a normal aldosterone/renin ratio of 40.0 pmol/mU (0-91), with normal urinary metanephrines: normetadrenaline 0.64 umol/d (0-3), metadrenaline 0.3 umol/d (0-1.4) and 3-Methyoxytyramine 0.85 umol/d (057-2.39). Somewhat unexpectedly, however, she had an elevated morning serum cortisol of 622 nmol/l (<50) following an overnight dexamethasone suppression test (DST). A further low dose DST also resulted in high serum cortisol of 225 nmol/l on day 2, with an ACTH of 40 ng/l (0-46). These results confirmed that the source of her hypercortisolaemia was not the adrenal incidentaloma. The primary differential was now pituitary Cushing’s disease, a far stretch away from the initial indication for having a CT abdomen and investigating an adrenal lesion.

Results and treatment: The patient went on to have further tests supportive of this, including a high-dose DST with >50% serum cortisol suppression recorded (day 0: 963 nmol/l; day 2: 345 nmol/l) and a dynamic MRI, revealing a 3 mm left-sided pituitary microadenoma with medialisation of the cavernous carotid artery. Inferior petrosal sinus sampling confirmed pituitary driven Cushing’s with left lateralisation. After discussion about the increased risk of surgery, she subsequently opted for a surgical resection of her pituitary tumour and commenced hydrocortisone replacement for low day 3 post-op cortisol. Histology showed a sparsely granulated lactotroph adenoma with low Ki67 but further histology review is awaited. Reassuringly, a short synacthen test performed 3 weeks post-operatively confirmed adequate adrenal response to ACTH stimulation, and the ongoing plan is to wean hydrocortisone, and reassess for hypercortisolaemia.

Conclusions and points for discussion: In conclusion, this is a remarkable case of a patient being diagnosed with pituitary Cushing’s after discovering an adrenal incidentaloma on CT, performed for an unrelated presenting complaint of melaena. It demonstrates the value of detailed history taking and stepwise testing for hypercortisolism.