Pheochromocytoma & Paraganglioma

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07/02/23

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Catecholamines: https://www.youtube.com/watch?v=Y-OB77dquX0
Neuroendocrine tumors: https://www.youtube.com/watch?v=I6G_Cd7zkQ8
Hypertension: https://www.youtube.com/watch?v=Ln1dExQ-U8A
Clonidine suppression test: https://www.youtube.com/watch?v=WoOVWI6wWAI

Pheochromocytoma is a tumor that arises from chromaffin cells present in the adrenal medulla or paraganglion cells. Paragangliomas are neuroendocrine neoplasms, derived from paraganglia of the sympathetic and parasympathetic nervous systems. They can arise in any location where paraganglia normally reside.

In 90% of the cases, pheochromocytoma is sporadic, but in 10% of patients, it is familial and associated with syndromes like Von Hippel–Lindau syndrome, type 1 neurofibromatosis, and multiple endocrine neoplasia syndromes type IIA & type IIB with an autosomal dominant mode of transmission.

Pheochromocytoma is a rare neuroendocrine disorder. Its incidence is about 0.1% to 0.3% in the hypertensive population.
Its incidence is equal in both genders.
It's usually diagnosed between the age of 30 to 50, but pheochromocytoma due to genetic predisposition can present earlier.

Pheochromocytoma can be asymptomatic and diagnosed by further workup of an adrenal incidentaloma. It can present with vague symptoms like a headache (50%), palpitations (60%), and diaphoresis (50%) that can lead to a paroxysmal hypertensive crisis due to increased catecholamine production. Other associated symptoms include pallor (40%), nausea (40%), tremor, trembling, fatigue (40%), anxiety, fever, pain, and flushing (20%). Characteristically, these symptoms are paroxysmal and may be precipitated by abdominal exertion, such as heavy lifting or performing the Valsalva maneuver. Almost 90% of the population with pheochromocytoma has hypertension.

If there is clinical suspicion of a pheochromocytoma, then initial assessment starts with biochemical laboratory testing.
Plasma free metanephrine or 24-hour urinary fractioned metanephrine testing is recommended; both can be done as an initial screen.
The sensitivity is almost the same between these two biochemical tests, but there is a difference in the specificity. The plasma test (89%) is more specific than a urine test (69%).

Credit:
Stockking @ freepik.com
Urinary vanillylmandelic acid is also used, but it is not as sensitive (64%).

Once metanephrine levels are 4-fold high from the normal reference value, then the next goal is to localize the hormone-secreting tumor.
The problem arises when the metanephrine levels are minimally elevated or equivocal. In that circumstance, the clonidine suppression test can help with the diagnosis. In this test, a baseline specimen for plasma catecholamines is collected and Clonidine hydrochloride (0.3 mg) is given orally. Blood for catecholamines is again collected at 180 minutes. Failure to suppress plasma catecholamines indicates autonomous release from a tumor.

The gold standard treatment of pheochromocytoma is surgical resection. An interprofessional team is required for management. It is mandatory to block catecholamine effect before surgery to prevent hypertensive crises and arrhythmias even in the patients who are normotensive or asymptomatic. There is no particular preference for one drug over another to prevent hypertensive crises. Any alpha-adrenoceptor antagonist, a calcium-channel blocker, or angiotensin-receptor blocker can be used. Calcium channel blockers or β-adrenergic blockers are indicated for the prophylactic treatment of arrhythmias.

Reference:
Asa SL, Ezzat S, Mete O. The Diagnosis and Clinical Significance of Paragangliomas in Unusual Locations. J Clin Med. 2018 Sep 13;7(9):280. doi: 10.3390/jcm7090280. PMID: 30217041; PMCID: PMC6162705.

Image credit: Kjpargeter / Freepik @ http://www.freepik.com

PDQ Adult Treatment Editorial Board. Adrenocortical Carcinoma Treatment (Adult) (PDQ®): Patient Version. 2020 May 20. In: PDQ Cancer Information Summaries [Internet]. Bethesda (MD): National Cancer Institute (US); 2002-. [Figure, Anatomy of the adrenal gland...] Available from: https://www.ncbi.nlm.nih.gov/b....ooks/NBK65782/figure
Case courtesy of Assoc Prof Frank Gaillard, Radiopaedia.org, rID: 10816
http://www.flickr.com/photos/5....8937697@N00/30788855
Utiger, Robert D.. "Pheochromocytoma". Encyclopedia Britannica, Invalid Date, https://www.britannica.com/sci....ence/pheochromocytom Accessed 10 March 2021.