A pheochromocytoma (also phaeochromocytoma, English spelling) is a tumor of the medulla of the adrenal glands originating in the chromaffin cells, which secretes excessive amounts of catecholamines, usually epinephrine and norepinephrine. Extra-adrenal paragangliomas (often described as extra-adrenal pheochromocytomas) are closely related, though less common, tumors that originate in the ganglia of the sympathetic nervous system and are named based upon the primary anatomic site of origin. more...
Up to 25% of pheochromocytomas may be familial. Mutations of the genes VHL, RET, NF1, SDHB and SDHD are all known to cause familial pheochromocytoma/extra-adrenal paraganglioma.
The signs and symptoms of a pheochromocytoma are those of sympathetic nervous system hyperactivity:
- elevated heart rate
- elevated blood pressure
- anxiety often resembling that of a panic attack
A pheochromocytoma can also cause resistant arterial hypertension. A pheochromocytoma can be fatal if it causes malignant hypertension, or severely high blood pressure.
The diagnosis can be established by measuring catecholamine and metanefrine in plasma or urine. One diagnostic test used in the past for a pheochromocytoma is to administer clonidine (Catapres®), a centrally-acting alpha-2 agonist used to treat high blood pressure. Clonidine mimics catecholamines in the brain, causing it to reduce the activity of the sympathetic nerves controlling the adrenal medulla. A healthy adrenal medulla will respond to clonidine by reducing catecholamine production; the lack of a response is evidence of pheochromocytoma. Another test is for the clinician to press gently on the adrenal gland. A pheochromocytoma will often release a burst of catecholamines, with the associated signs and symptoms quickly following.
Pheochromocytomae occur most often during young-adult to mid-adult life. Less than 10% of pheochromocytomas are malignant (cancerous).
These tumors can form a pattern with other endocrine gland cancers which is labelled multiple endocrine neoplasia (MEN). Pheochromocytoma may occur in patients with MEN 2a and MEN 2b.
The differential diagnosis of pheochromocytoma includes:
- Anxiety disorders
- Carcinoid tumor
- Essential hypertension
- Paroxysmal supraventricular tachycardia
- Renovascular hypertension
Surgical resection of the tumor is the treatment of first choice.
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