Basic Science and Pathophysiology

The manifestations of phaeochromocytoma are due mostly to the increased abnormal secretion of catecholamines, principally epinephrine, but also norepinephrine and dopamine. 

The relative amounts of catecholamines secreted can differ between tumours and this determines the clinical picture. The catecholamines can also be released episodically. 

There are several proposed mechanisms for this including direct pressure, medications and changes in tumour blood flow [6].

The effects of Epinephrine and Norepinephrine are caused by agonism of alpha and beta adrenoceptors and are detailed below [7].

• Glycogenolysis in liver and skeletal muscle
• Mobilisation of free fatty acids
• Increased serum lactate
• Stimulation of metabolic rate
• Increased force and rate of contraction of the heart
• Both cause vasoconstriction, but epinephrine dilates vessels in skeletal muscle and liver, normally leading to a decrease in overall systemic vascular resistance
• Increase in alertness and evokes feelings of anxiety and fear
• Rise in plasma glucose

Dopamine, when injected, produces renal and mesenteric vascular dilatation.  It also has positive inotropic effects and normally leads to an increase in systolic blood pressure.