Phaeochromocytoma

Question 1

Pathophysiology

Answer 1

Adrenaline is produced by the “chromaffin cells” in the adrenal glands. A phaeochromocytoma is a tumour of the chromaffin cells that secretes unregulated and excessive amounts of adrenaline. Adrenaline is a “catecholamine” hormone and neurotransmitter that stimulates the sympathetic nervous system and is responsible for the “fight or flight” response. In patients with a phaeochromocytoma the adrenaline tends to be secreted in bursts giving periods of worse symptoms followed by more settled periods.

Question 2

Diagnosis

Answer 2

24 hour urine catecholamines
Plasma free metanephrines
Measuring serum catecholamines is unreliable as this will naturally fluctuate and it will be difficult to interpret the result. Measuring 24 hour urine catecholamines gives an idea of how much adrenaline is being secreted by the tumour over the 24 hour period.

Adrenaline has a short half life of only a few minutes in the blood, whereas metanephrines (a breakdown product of adrenaline) have a longer half life. This makes the level of metanephrines less prone to dramatic fluctuations and a more reliable diagnostic tool.

Question 3

How does phaeocytoma present?

Answer 3

Signs and symptoms tend to fluctuate with peaks and troughs relating to periods when the tumour is secreting adrenaline.

Anxiety
Sweating
Headache
Hypertension
Palpitations, tachycardia and paroxysmal atrial fibrillation

Question 4

How to manage

Answer 4

Alpha blockers (i.e. phenoxybenzamine)
Beta blockers once established on alpha blockers
Adrenalectomy to remove tumour is the definitive management
Patients should have symptoms controlled medically prior to surgery to reduce the risk of the anaesthetic and surgery.