Pheochromocytoma

Pheochromocytoma is a catecholamine-producing neuroendocrine tumour arising from chromaffin cells in the adrenal medulla. Its extra-adrenal counterpart is a paraganglioma. Excess norepinephrine and epinephrine produce episodic or sustained vasoconstriction and cardiac stimulation, so the patient may develop abrupt hypertension, tachycardia, headache, sweating, palpitations, and a sense of impending panic. The symptoms make physiological sense. Alpha-adrenergic stimulation tightens vascular smooth muscle and raises systemic vascular resistance. Beta-1 stimulation increases heart rate and contractility. Together, these effects can produce a dramatic blood-pressure surge with a pounding heartbeat and severe headache. Catecholamine effects can also increase blood glucose through glycogen breakdown. Tumour release may occur in bursts. A patient can therefore look comfortable and have an acceptable blood pressure between episodes, then become acutely symptomatic minutes later. Physical activity, positional change, abdominal manipulation, anaesthesia, and certain medications can precipitate release. A panic-like presentation does not make the hypertension benign; the blood pressure recorded during the episode is a critical part of the pattern.