An interesting case of Cushing’s syndrome in a patient with phaeochromocytoma.
Paul Dent, SN Ali, J Pomroy, Celine Haines, T Vakilgilani, FF Palazzo, J Jackson, A Sam, K. Meeran, E Hatfield.
A 59 year old lady presented to the Urologists with a history of abdominal pain. As part of her investigations, she had a CT abdominal scan which identified a 41mm left para-aortic lesion and a 25mm nodule in the posterolateral limb of the left adrenal. She was then noticed to have hypertension and on further enquiry, gave a six-month history of palpitations and hot sweats. A phaeochromocytoma was suggested by raised 24hr urinary catecholamines: noradrenaline (3.08), raised adrenaline (0.43), and raised plasma catecholamine levels: noradrenaline (79.0) and adrenaline (7.0). She was started on alpha-blockade with phenoxybenzamine and subsquently beta-blockade with propranolol. A NM MIBG Iodine 123 whole body scan confirmed the lobulated retroperitoneal 41mm paraganglioma was MIBG avid and its medial margin abutted and was thought to arise from the left adrenal gland. The small nodule in the left adrenal appeared to have characteristics of a lipid rich adenoma. On discussion in the Adrenal MDT, it was decided that both lesions should be removed at time of surgery.
Although initially she did not exhibit any clinical features, other than central obesity and perhaps hypertension, to suggest Cushing’s syndrome, a low dose dexamethasone suppression test (LDDST) was performed in order to exclude cortisol co-secretion from the lesions. This revealed a high midnight cortisol (172) and failure to suppress at 48hrs (506), ACTH was 22.2. Repeat LDDST confirmed failure to suppress cortisol at 48hrs (782) and ACTH was 83.5. A 24hr urinary collection showed high cortisol levels (418). Interestingly, over a 6 week period whilst under our care, ACTH levels have been serially increasing [ACTH level (2 months earlier) on presentation was undetectable (<5.0) and subsequent ACTH levels have been: 22.2, 32.2, 83.5, 240]. She has become increasingly clinically Cushingoid, now with a clear buffalo hump and easy bruising. She has normal glucose levels. Together with the new development of hypokalaemia suggest an ectopic secretion of ACTH, with the most probable source from the phaeochromocytoma. Metyrapone was initiated and titrated to 1g tds. Cortisol levels are down to 150 - 300. Following adrenalectomy, her ACTH has fallen to 9.4 and she is well with a stable blood pressure off alpha and beta blockade.
ACTH-secretion by a phaeochromocytoma was first described in 1964 and to date, including our case there are some 30 reported cases.