Endocrine Abstracts

Dopamine agonists can falsely elevate plasma and urinary metanephrines, thus making the diagnosis of pheochromocytomas in patients taking these medications challenging. We present the case of an 80-year-old female care home resident with a background of hypertension, Parkinson’s disease (PD), dementia and pernicious anaemia. She presented with weight loss, unilateral leg swelling and abdominal distension. A computed tomography (CT) showed a 5.6 cm heterogeneously enhancing left adrenal mass. The patient reported no symptoms consistent with a phaeochromocytoma and the physical examination revealed no stigmata of an endocrinopathy. Biochemistry showed significantly raised plasma metanephrine, normetanephrine and 3-methoxytyramine, favouring the diagnosis of a pheochromocytoma over a false positive result due to carbidopa/levodopa. Urinary metanephrines were also high and an iodine-123 metaiodobenzylguanidine (MIBG) scan revealed increased radiotracer uptake in the left adrenal, confirming the diagnosis. Surgical treatment was discussed with the patient and her daughter and in view of significant frailty, comorbidities, high surgical risk and absence of symptoms, it was pragmatically agreed to manage her conservatively. Medical treatment with alpha blockers followed by beta blockers was not thought to be in her best interest due to risk of postural hypotension and falls in presence of PD and because blood pressure was well controlled on ramipril. An interval CT scan did not show any change in the size or characteristics of the lesion, further supporting conservative management. She is currently being followed up in the endocrine clinic. This case emphasises the need to interpret measurements of catecholamines and their metabolites in the context of confounding medications like carbidopa/levodopa, which can falsely elevate plasma and urine metaneprhines, especially 3-methoxythyramine and urinary dopamine. Clinicians need to be mindful of such a pitfall, not rely on biochemical or radiological diagnosis only and consider early functional imaging with MIBG scintigraphy, gallium-68 DOTATATE positron emission tomography (PET) or fludeoxyglucose-PET, amongst others. We suspect that our patient’s lesion grew to such a large size due to her lack of hormone-related symptoms as symptomatic phaeochromocytomas are often diagnosed when relatively smaller. Apart from a diagnostic challenge, patients with PD and other comorbidities can also be challenging to manage, as they are often high-risk surgical candidates, and adrenalectomy, which would otherwise be a gold standard curative treatment, is not an option. Shared decision making, multidisciplinary team approach with a view to provide individualised, holistic care and good communication with patients and their families are key elements in management.