Disorders of Adrenal Medulla

Question 1

For the adrenal medulla:

• State embryological origin
• State what it secretes

Answer 1

• Neural crest cells
• Secretes adrenaline, noradrenaline, dopamine and their metabolites (metanephrines, nor-metanephrines and 3-methoxytyramine)

*SEE MEH FOR MORE DETAIL

Question 2

What cells in adrenal medulla produce catecholamines?

Answer 2

Chromaffin cells

Question 3

What is a phaechromocytoma

Answer 3

Tumour of chromaffin cells that secretes unregulated excessive amounts of adrenaline. The adrenaline secretion is paroxysmal (in bursts) giving periods of worse symptoms followed by more settled periods.

Question 4

Discuss the 10% rule to describe the patterns of tumours in phaechromocytomas

Answer 4

• 10% bilateral
• 10% malignant
• 10% outside adrenal gland
• 10% familial

Question 5

If a phaeochromocytoma arises from extra-adrenal chromaffin tissue, what is this called?

Answer 5

Paragangliomas

Question 6

State some risk factors for devloping phaeochromocytoma

Answer 6

• MEN syndrome type 2
• Von Hipple-Landau disease
• Succinate dehydrogenase (SDH) subunit B,C and D gene mutations

Question 7

State some signs &symptoms of phaeochromocytoma

Answer 7

Symptoms & signs fluctuate/are episodic dependent on if tumour is secreting catecholamines…

• Headaches
• Sweating
• Palpitations
• Anxiety
• Hypertension
• Paroxysmal AF

Question 8

What is the triad of symptoms in phaeochormocytoma?

Answer 8

• Headaches
• Sweating
• Palpitations/tachycardia

Question 9

Discuss what investigations you would do if you suspect a pt has a phaeochromocytoma, include:

• Bedside
• Bloods
• Imaging
• Others

*Justify each where appropriate

Answer 9

Bedside

• 24hr urine metanephrines (would give this as exam answer)

Bloods

• FBC: may show raised WCC
• Plasma metanephrines

Imaging

• CT or MRI of abdomen: localise tumour
• CT or MRI of full body if tumour is not localised
• MIBG scans: used if can’t locate tumours on MRI
• PET scan: localise tumour

Others

• Genetic testing: if pt presents at young age, has multifocal, malignant or extra-adrenal tumours. If pts genetic test is positive they should have annual screenign and first degree relatives should be tested

Question 10

Adrenaline has a short half life whereas metanephrines (breakdown products of adrenaline) have a longer half life hence level of metanephrines are a more reliable diagnostic tool; true or false?

Answer 10

True

Question 11

Discuss the management of pheochromocytoma

Answer 11

• Alpha blockers e.g. phenoxybenzamine
• Beta blockers once established on alpha blockers e.g. propranolol
• Adrenalectomy to remove tumour is the definitive treatment but

*NOTE: pts should have symptoms controlled medically prior to surgery to reduce risk of anaesthetic & surgery

Question 12

Explain why you must never give beta blockade before pt is established on alpha blockade in phaeochromocytoma. To help you figure out the answer, consider:

• Why pts need alpha blocker
• Why pts may ned beta blocker
• Explain what could occur if you give beta blocker prior to alpha blocker

Answer 12

• Alpha blockers stop catecholamine induced vasoconstriction to decrease hypertension
• Since you are opposing vasoconstriction you can get decrease in BP and reflex tachycardia- this is why pt may need alpha and beta blockage
• If you give beta blocker first, it will prevent beta-2 mediated vasodilation. This could lead to profound unopposed alpha mediated vasoconstriction leading to hypertensive crisis and/or pulmonary oedema

Question 13

State some potential complications of a phaeochromocytoma

Answer 13

• Acute hypertensive crisis
  
  • This may lead to neurological complications (hypertensive encephalopathy)
• Hyperglycaemia
• Pulmonary oedema
• Cardiac arrhythmias
• Death
• Post operative complications e.g. hypotension, arrhythmias