Endocrine Abstracts

The diagnosis of Pheochromocytomas often poses a great challenge. We report a case of pseudo-pheochromocytoma causing challenges in the clinical diagnosis. A 35-year old gentleman with high BMI, was admitted with worsening headache, visual field defects and accelerated hypertension. MRI pituitary and biochemical profiling revealed a non-functioning pituitary macroadenoma with optic chiasm compression, warranting urgent surgical intervention, vindicating an endocrinology referral and in parallel, investigating for secondary hypertension. Initial investigations were highly suggestive of Pheochromocytoma, including a significantly elevated 24-h urinary catecholamines and subsequent MIBG scan showing bilateral positive tracer uptake. CT adrenals however did not identify any lesions. Discordant results engendered further exploration to identify the presence of confounding factors including preanalytical drug interference. No medication interferents were identified. On the contrary, he was identified as high risk for obstructive sleep apnoea (OSA) and subsequently, he was started on home non-invasive ventilation. Two different plasma metanephrines samplings came back within normal limit, leading to confidence of proceeding to Trans-sphenoidal surgery safely. 24-h urinary catecholamines sampling was repeated to check on OSA as a confounding factor for the discrepant results. Guidelines recommend the measurement of plasma or 24 h urinary metanephrines as the initial biochemical test, positive tests to trigger further urgent investigations, as delay in treatment is often debilitating. The supraphysiologic effects of endogenous catecholamines in OSA is well-established, acknowledging it as an independent confounding factor in biochemical assessment of pheochromocytomas. Overlapping clinical features like headaches and hypertension are common, thereby making the diagnosis more challenging. Clinical symptoms, blood pressure and catecholamine levels tend to improve with treatment of the OSA. This case highlighted the importance of identifying confounding factors prior to organising expensive biochemical investigations and imaging studies, and hence endorsing the pitfalls involved in the diagnosis of this challenging condition deservedly known as’ the great masquerader”.