Endocrine Abstracts

Introduction: Phaeochromocytomas commonly present with episodes of sweating, palpitations, and hypertension. Urinary catecholamines measurement is the most common screening test for suspected phaeochromocytoma in the UK. We report a series of three cases in which the reason for hypertension and raised catecholamines was not a phaeochromocytoma and treating the underlying condition corrected the clinical and biochemical abnormality.

Cases: Three patients were referred to the endocrine clinic with symptoms suggestive of phaeochromocytoma, and isolated elevation in 24 h urinary Noradrenaline (NA) levels. (Table 1) Imaging for phaeochromocytoma was negative.

On further questioning, all patients mentioned a history of snoring, and daytime somnolence. Polysomnography suggested severe degree of sleep apnoea (OSA) with Aponea/Hypopnea Index (AHI) of 52 events/h in case1 and 40 events/hour in case 2. CPAP treatment resulted in better BP control, symptomatic improvement and normalisation of urinary catecholamines. In case 3, the patient managed to lose 6 kg in weight and his symptoms improved with an AHI of 10.4 events/hour. Repeat 24 h urinary catecholamine levels after weight loss were normal.

Discussion: OSA is characterized by short intervals of partial or complete upper airway obstruction during sleep resulting in blood oxygen desaturation. Oxygen desaturation may explain the increased sympathetic activity widely demonstrated in patients with OSA. Patients with OSA could present in a similar picture to phaeochromocytoma.

Conclusions: OSA should be considered in the differential diagnosis of phaeochromocytoma in patients with raised catecholamines and negative imagining for phaeochromocytoma. Treatment for OSA results in normalization of raised catecholamines and improvement in patients’ symptoms and blood pressure.