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Phaeochromocytoma & Paraganglioma | MRCP Part 1

TL;DR

Endo: Phaeochromocytoma & Paraganglioma are catecholamine-secreting tumours frequently tested in MRCP Part 1, especially for diagnosis, genetics, and perioperative management. Suspect them in episodic hypertension with headache, sweating, and palpitations; confirm with plasma metanephrines. Always initiate alpha-blockade before beta-blockade to avoid hypertensive crisis. Genetic syndromes and biochemical testing strategies are common exam traps.


Why this matters

Phaeochromocytoma and paraganglioma (PPGL) are high-yield endocrine conditions for MRCP Part 1, combining clinical recognition, biochemical interpretation, genetics, and safe pharmacological management. Questions often focus on the correct diagnostic pathway and the critical principle of pre-operative preparation.

For a broader roadmap, see the MRCP Part 1 overview and integrate this topic into your endocrine revision strategy.


Core sections

1. Definitions and classification

  • Phaeochromocytoma: Tumour arising from chromaffin cells of the adrenal medulla

  • Paraganglioma: Extra-adrenal tumour from autonomic ganglia

Functional classification:

  • Sympathetic → catecholamine-secreting (clinically significant)

  • Parasympathetic → usually non-secretory (head & neck tumours)

2. Clinical features: recognise the pattern

Classic triad:

  • Headache

  • Sweating

  • Palpitations

Other key features:

  • Sustained or paroxysmal hypertension

  • Pallor or flushing

  • Anxiety or panic attacks

  • Orthostatic hypotension (due to chronic vasoconstriction and volume depletion)

Exam insight: The triad is classic but not always present—hypertension is the most consistent finding.

3. Biochemical diagnosis (most tested concept)

Test

Role

Key Exam Point

Plasma free metanephrines

Screening

Most sensitive test

24-hour urinary metanephrines

Confirmation

High specificity

Plasma catecholamines

Limited use

Not first-line

Clonidine suppression test

Rare

Specialist setting

Why metanephrines? Tumours continuously convert catecholamines into metanephrines, making them more reliable markers than episodic catecholamine release.

4. Imaging and localisation

  • CT abdomen: First-line for localisation

  • MRI: Preferred in pregnancy, children, and extra-adrenal suspicion

  • Functional imaging:

    • MIBG scintigraphy

    • PET scanning (FDG or DOTATATE)

5. Genetics and syndromic associations

Up to 40% of PPGL cases are hereditary, making genetics highly testable.

Key syndromes:

  • MEN2 (RET mutation)

  • Von Hippel–Lindau (VHL)

  • Neurofibromatosis type 1 (NF1)

  • Succinate dehydrogenase (SDH) mutations

Exam pearls:

  • Bilateral adrenal tumours → MEN2 or VHL

  • SDHB mutation → higher risk of malignancy

6. Pre-operative management (critical safety concept)

Stepwise approach:

  1. Start alpha-blocker (phenoxybenzamine or doxazosin)

  2. Ensure adequate hydration and salt intake

  3. Add beta-blocker only after alpha-blockade

🚫 Never give beta-blocker first → causes unopposed alpha stimulation → hypertensive crisis

7. Definitive treatment

  • Surgical resection (usually laparoscopic adrenalectomy)

  • Pre-operative optimisation is essential to reduce perioperative risk

8. Malignancy and prognosis

  • Defined by presence of metastases, not histology

  • Common metastatic sites: bone, liver, lungs

  • SDHB mutations → poorer prognosis

9. High-yield revision checklist

  1. Episodic hypertension + triad → suspect PPGL

  2. Plasma metanephrines = best initial test

  3. CT/MRI for localisation

  4. Always consider genetic syndromes

  5. Alpha-blockade before beta-blockade

  6. Surgery is definitive treatment

  7. Lifelong follow-up required

  8. Malignancy = metastasis

Student studying about mrcpc part1

Practical examples / mini-cases

MCQ-style question: A 42-year-old man presents with episodic headaches, sweating, and palpitations. Blood pressure spikes to 200/110 mmHg. Plasma metanephrines are elevated. He is started on propranolol and develops worsening hypertension.

What is the most likely explanation?

Answer: Unopposed alpha-adrenergic stimulation

Explanation: Beta-blockade without prior alpha-blockade removes vasodilatory beta effects, leaving alpha-mediated vasoconstriction unopposed—resulting in hypertensive crisis. This is a classic MRCP Part 1 pitfall.


Common pitfalls (5 bullets)

  • Starting beta-blockers before alpha-blockade

  • Ordering catecholamines instead of metanephrines

  • Missing hereditary syndromes in young patients

  • Assuming all tumours are adrenal in origin

  • Misclassifying malignancy based on histology


FAQs

1. What is the best initial test for suspected phaeochromocytoma?

Plasma free metanephrines are the most sensitive initial test. Urinary metanephrines are used for confirmation.

2. Why must alpha-blockade be given first?

It prevents life-threatening hypertensive crises caused by catecholamine-induced vasoconstriction.

3. Which syndromes are associated with phaeochromocytoma?

MEN2, VHL, NF1, and SDH mutations are key associations tested in MRCP.

4. How is malignancy defined?

By the presence of metastases rather than histological features.

5. When should genetic testing be considered?

In all patients, especially those with early onset, bilateral tumours, or family history.


Ready to start?

Strengthen your endocrine preparation with structured learning and active recall. Begin with the MRCP Part 1 overview, practise using Free MRCP MCQs, and assess readiness with a Start a mock test.

For related topics, review adrenal insufficiency and thyroid disorders within your revision plan to build integrated understanding.


Sources

 
 
 

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