DISORDER OF ADRENAL MEDULLA

Question 1

WHAT IS A PHAEOCHROMOCYTOMA?

Answer 1

Catecholamine secreting tumour arising from the adrenal medulla.

Question 2

WHAT IS A PARAGANGLIOMAS?

Answer 2

Catecholamine secreting tumour arising from extra-adrenal chromaffin tissue

Question 3

WHAT ARE THE CLINICAL FEATURES OF THESE TUMOURS?

Answer 3

1) headache
2) sweating
3) palpitations
4) pallor
5) anxiety/ panic attacks
6) hypertension - >90% of patients

Question 4

WHAT ARE THE COMPLICATIONS OF PHAEOCHROMOCYTOMA?

Answer 4

1) hypertensive crisis
2) encephalopathy
3) hyperglycaemia
4) pulmonary oedema
5) cardiac arrhythmias

Question 5

WHAT ARE THE INVESTGIATIONS FOR PHAEOCHROMOCYTOMA/ PARAGANGLIOMAS?

Answer 5

1) 24 hour urinary catecholamines - elevated
2) plasma metanephrines (breakdown product of catecholamines) - elevated
3) CT/ MRI abdomen - localise tumour
4) Whole body MRI - if tumour is not localised

Question 6

WHAT IS THE DEFINITIVE MANAGEMENT?

Answer 6

1) Surgical excision - laparoscopically or through an open procedure

Question 7

WHAT IS THE PHARAMCOLOGICAL MANAGEMENT AND IN WHICH ORDER SHOULD MEDICATION BE GIVEN AND WHY?

Answer 7

1) Phenoxybenzamine (alpha blocker) - control hypertension and sweating
2) Bisoprolol (beta blocker) - control reflex tachycardia (as a result of phenoxybenzamine)

Alpha- blocker first then beta-blocker to avoid unopposed alpha-adrenergic stimulation and risk of hypertensive crisis.

Question 8

WHY DOES PHENOXYBENZAMINE CAUSE REFEX TACHYCARDIA?

Answer 8

Non selective alpha receptor antagonist therefore they act on alpha 1 and alpha 2 receptors.
Alpha 1 on vascular smooth muscle is responsible for vasoconstriction
Alpha 2 receptors inhibit sympathetic activity.
Therefore, sympathetic activity is inhibited leading to a drop in blood pressure, the heart beats faster in an attempt to raise it (reflex tachycardia).