Posted by e-Medical PPT Sunday, September 26, 2010
A pheochromocytoma is a neuroendocrine tumor of the medulla of the adrenal glands (originating in the chromaffin cells), or extra-adrenal chromaffin tissue that failed to involute after birth and secretes excessive amounts of catecholamines.Extra-adrenal pheochromocytomas or paragangliomas are closely related, though less common, tumors that originate in the ganglia of the sympathetic nervous system.Up to 25% of pheochromocytomas may be familial.Pheochromocytoma is a tumor of the multiple endocrine neoplasia syndrome, type IIA and type IIB. The other component neoplasms of that syndrome include parathyroid adenomas, and medullary thyroid cancer.The signs and symptoms of a pheochromocytoma are those of sympathetic nervous system hyperactivity.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 catecholamines and metanephrines in plasma (blood) or through a 24-hour urine collection.Imaging by computed tomography or a T2 weighted MRI of the head, neck, and chest, and abdomen can help localize the tumor.Either surgical option requires prior treatment with the non-specific and irreversible alpha adrenoceptor blocker Phenoxybenzamine.

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