Endocrine Abstracts

75 male was referred to endocrine service with incidental pituitary macroadenoma measuring 4.2×3.1×3.3 cm noted on MRI-C-Spine done for ankylosing spondylitis with Atlanto-axial joint instability. He had reduced secondary sexual characteristics and left quadrantanopia. Endocrine studies confirmed thyrotroph and gonadotroph failure but normal lactotroph and HPA axis. He underwent trans-sphenoidal tumour resection followed by external beam radiation due to tumour residuum. His quadrantanopia resolved completely and he was started on annual pituitary assessment. 2 years later he developed palpitations and collapsed following Synacthen injection for short Synacthen test (SST). He made full recovery and initial work up demonstrated no clear cause. A repeat SST 6 month later resulted in palpitations and near collapse. An evolving history of frequent episodes of palpitations and sweating accompanied by headache over the previous months was noted, which raised suspicion of pheochromocytoma. Plasma metanephrines then were marginally elevated (metadrenaline 1140 (80–510) pmol/l, normetadrenaline 3833 (120–1180) pmol/l). This rose further in the following 3 months (metadrenaline 3008 pmol/l, normetadrenaline 5387 pmol/l) and 24 urine analsysis demonstrated raised indices to creatinine (metadrenalines/creatinine 1.14 (0–0.3) umol/mmol, normetadrenaline/creatinin 0.76 (0–0.35) umol/mmol). CT-abdomen demonstrated a suspicious L-adrenal mass measuring 4.5×4.3 cm. MIBG scan showed uptake in the region of L-adrenal consistent with a neuroendocrine tumour. Alpha-blockade was established and patient later underwent L-adrenalectomy. Histopathology confirmed pheochromocytoma. Metanephrines normalised post-operatively but SST demonstrated inadequate adrenal response. He is currently on glucocorticoid replacement and annual pituitary assessment. This case demonstrates synacthen-induced pheochromocytoma crisis. There are several case reports of exogenous glucocorticoid-induced pheochromocytoma crises but no reports of Synacthen/ACTH-induced crisis were found. The likely mechanism is the effect of glucocorticoid surge secondary to synacthen stimulation leading to augmented effect on enzymes involved in catecholamine biosynthesis and release, e.g. phenylethanolamine N-methyltransferase (PNMT).