Phaeochromocytoma Flashcards
Phaeochromocytoma - Example Question
A 43 year old man has been referred to endocrinology clinic for blood pressure investigation and management. Over the past year the patient has had a persistently raised blood pressure between 170/100mmHg and 180/110mmHg. Despite starting the patient on ramipril 5mg once daily four weeks ago the patient’s blood pressure on this visit remained raised at 164/93mmHg.
During the history taking part of the consultation the patient mentions that he has been troubled with headaches for the past year, and has noticed that his stool frequency has increased and his stools have become looser. He tells you that he’s rather embarrassed to admit that he’s been having flushing episodes, and feels that his clothes are much looser than they were 1 year ago.
On discussing his family history he mentions that both his mother and his father had to have cancerous lumps removed in their middle ages. His mother had a breast lump removed, and his father had some form of pancreatic mass removed.
On examination the patient is tall with a wide arm span. Examination of the cardiovascular system reveals only a minor tachycardia of 95bpm and a quiet systolic flow murmur not radiating to the carotids. Abdominal examination reveals no palpable masses, and examination of his lungs is completely normal.
The GP had previously arranged a 24h urinary catecholamine test; results are as follows:
Total urine catecholamines 210mcg/24hr. This is raised.
As a follow up to this test the GP had arranged a CT of the patient’s abdomen and pelvis which is reported as normal apart from a few incidental simple renal cysts.
Urinalysis in clinic today shows: Leucocytes - Blood - Glucose + Ketones -
Which test is most likely to elucidate the cause of the patient’s hypertension?
Pentagastrin stimulation test 24h urinary HIAA MRI renal angiography GH, IGF-1 and 'gut hormones' > MIBG (metaiodobenzylguanidine) scan
This question tests the candidates knowledge of causes of secondary hypertension.
The best way of narrowing down to the correct answer in this question is to actually look at what the answers are suggesting:
Pentagastrin stimulation test = Test for medullary carcinoma of the thyroid (associated with MEN2 - multiple endocrine neoplasia)
24h Urinary HIAA = Screening for carcinoid
MRI renal angiography = Test for renal artery stenosis
GH, IGF-1 and ‘gut hormones’ = Test for pancreatic malignancy associated with MEN1
MIBG scan = Test for phaeochromocytoma
While this patient might well have MEN2 (as suggested by the patients body habitus and features consistent with phaeochromocytoma), medullary thyroid cancer would be unlikely to cause his blood pressure issues. Therefore the pentagastrin stimulation test, where one injects the patient with pentagastrin and looks for an abnormally high release of calcitonin as a response, is not a suitable first test. It may well be considered if the patient is diagnosed with a phaeochromocytoma to rule out medullary thyroid cancer as part of MEN 2.
The patient does have a few features consistent with carcinoid syndrome, for example the episodic flushing and increased stool frequency. However carcinoid syndrome doesn’t present with these symptoms until it has metastasised to the liver, and this patient has had a normal CT scan of his abdomen making this a less likely diagnosis.
MRI renal angiography is used to diagnose renal artery stenosis; this patient has far too many other endocrine features for this to be renal artery stenosis. In addition the fact his blood pressure has not got worse with angiotensin converting enzyme inhibitors makes the diagnosis less likely.
Testing for gut hormones would be done in a patient in whom you were considering a diagnosis of pancreatic neoplasm as part of MEN1.
This leaves the MIBG (metaiodobenzylguanidine) scan. The patient has raised levels of total urinary catecholamines, suggesting a diagnosis of phaeochromocytoma, however, his CT scan show's no evidence. As you may be aware there is a rule of 10 that is commonly used to describe phaeochromocytoma, in that: 10% are malignant 10% are bilateral 10% are familial 10% are in children 10% are extra-adrenal
The other sites that phaeochromocytomas can present include:
Anywhere alone the sympathetic chain which runs alongside the spinal cord, the distal aorta, ureters and urinary bladder.
The MIBG scan uses radioactive iodine as a tracer for phaeochromocytoma tumour cells, which is detected through the use of a gamma camera., making it the next test that should be used in diagnosing this patient’s phaeochromocytoma, i.e. the cause of his hypertension.
Kumar & Clark’s Clinical Medicine Eight Edition page 778
HTN - 2dry Causes
Hypertension: secondary causes
It is thought that between 5-10% of patients diagnosed with hypertension have primary hyperaldosteronism, including Conn’s syndrome. This makes it the single most common cause of secondary hypertension.
Renal disease accounts for a large percentage of the other cases of secondary hypertension. Conditions which may increase the blood pressure include: glomerulonephritis pyelonephritis adult polycystic kidney disease renal artery stenosis
Endocrine disorders (other than primary hyperaldosteronism) may also result in increased blood pressure:
phaeochromocytoma
Cushing’s syndrome
Liddle’s syndrome
congenital adrenal hyperplasia (11-beta hydroxylase deficiency)
acromegaly
Other causes include: NSAIDs pregnancy coarctation of the aorta the combined oral contraceptive pill steroids MAOI
Secondary HTN - Causes
The commonly listed causes of secondary hypertensions are listed below:
ENDOCRINE:
- Cushings
- Acromegaly
- Thyroid disease
- Hyperparathyroidism
ADRENAL:
- Conn’s Syndrome
- Adrenal Hyperplasia
- Phaeochromocytoma
RENAL:
- Diabetic Nephropathy
- Chronic glomerulonephritis/tubulointerstitial nephritis
- ADPKD
- Renovascular disease
CARDIOVASCULAR:
- Aortic Dissection
DRUGS:
- NSAIDs
- Oral Contraceptives
- Steroids
- Sympathomimetics
- Monoamine oxidase inhibitors
Phaeochromoctyoma - Ix
Do 24hour urinary metanephrines (NOT catecholamines)
3 x 24hr collections are needed as some patients have intermittently raised levels
Pheochromocytoma
= rare catecholamine secreting tumour
About 10% are familial and may be associated w MEN type II, Neurofibromatosis and von-Hippel-Lindau syndrome
Basics:
- Bilateral in 10%
- Malignant in 10%
- Extra-adrenal in 10% (most common site = organ of Zuckerland, adjacent to bifurcation of aorta)
Features:
- HTN (90% cases, may be sustained)
- Headaches
- Palpitations
- Sweating
- Anxiety
Tests:
- 24 hour urinary collection of metanephrines (97% sensitivity)
- this has replaced 24hr urinary collection of catecholamines (88% sensitivity)
Mx: - Surgery - definitive Mx The patient must be first however be stabilised w medial Mx given before: > alpha-blocker phenoxybenzamine > beta-blocker propranolol
PHaeochromocytoma = give PHenoxybenzamine (non-selective alpha-adrenoceptor antagonists) before beta-blockers
