Phaeochromocytoma

A catecholamine-secreting tumour of the adrenal medulla. Often found incidentally on biochemical screening or adrenal imaging. Roughly 5% of adrenal masses are phaeochromocytomas, and ~10% are extra-adrenal (paragangliomas). Rare in practice, a favourite in exams.

Clinical features

Classic paroxysms of:

• hypertension, headache, sweating, palpitations
• pallor/skin blanching
• a rising sensation or chest tightness (± angina)

In about half of cases the hypertension is continuous rather than paroxysmal.

Investigations

• Plasma free metanephrines and normetanephrines (primary screen) and/or 24-hour urinary metanephrines; 24-hour urinary free catecholamines are less sensitive. A single clearly normal metanephrine level excludes it; repeat mildly elevated results.
• False positives — antidepressants (TCAs, tetracyclics, noradrenaline reuptake inhibitors, SNRIs, MAOIs), sympathomimetics, and alpha/beta-blockers. Exercise, coffee, standing, stress/illness raise levels; paracetamol cross-reacts (avoid for a couple of days before testing).
• Imaging — abdominal CT for an adrenal mass once biochemistry is positive.

Management

Refer to endocrinology. Medical preparation is alpha-blockade first, then beta-blockade — never start a beta-blocker before alpha-blockade is established (unopposed alpha stimulation → hypertensive crisis). Definitive treatment is surgical removal.