Pheochromocytoma excess catecholamines

Metyrosine (23, a-methyl-L-tyrosine), a norepinephrine biosynthesis inhibitor, is in limited clinical use to help control hypertensive episodes and other symptoms of catecholamine overproduction in patients with the rare adrenal tumor pheochromocytoma (10). Metyrosine, a competitive inhibitor of tyrosine hydroxylase, inhibits the production of catecholamines by the tumor. Although metyrosine is useful in treating hypertension caused by excess catecholamine biosynthesis... 

Therapeutic uses Conditions of catecholamine excess such as pheochromocytoma Peripheral vascular disease Benign prostatic hypertrophy Same as phenoxybenzamine Primary hypertension Benign prostatic hypertrophy... 

The major clinical use of phenoxybenzamine is in the management of pheochromocytoma. Patients have many symptoms and signs of catecholamine excess, including intermittent or sustained hypertension, headaches, palpitations, and increased sweating. 

In contrast to phenoxybenzamine, phentolamine [fen TOLE a meen] produces a competitive block of ai and a2 receptors. The drug s action lasts for approximately 4 hours after a single administration. Like phenoxybenzamine, it produces postural hypotension and causes epinephrine reversal. Phentolamine had been used in the diagnosis of pheochromocytoma and in other clinical situations associated with excess release of catecholamines. Phentolamine-induced reflex cardiac stimulation and tachycardia are mediated by the baroreceptor reflex and by blocking the a2 receptors of the cardiac sympathetic nerves. The drug can also trigger arrhythmias and anginal pain and is contraindicated in patients with decreased coronary perfusion. 

In one patient who took 900 mg of phenelzine, there was a marked excess of urinary and plasma catecholamines, analogous to pheochromocytoma, and the patient was successfully managed with alpha-adrenoceptor antagonists (44). In another patient, who probably... 

Endocrine hypertension actually includes several diseases characterized by elevated blood pressure with causes that can be traced to an endocrine abnormality or actual injury. Two of the best known are pheochromocytoma and Cushing s syndrome. The former is characterized by a tumor that secretes excessive amounts of catecholamines, primarily epinephrine. This in turn increases vasomotor tone, resulting in a considerable pressure increase. Surgical removal of the tumor is curative. The latter is a disease of the adrenal cortex where tumors may also develop. The cortex is the site of corticosteroid production. Thus excessive production of aldosterone will act on the kidneys, causing retention of sodium and water. This increased blood volume is usually manifested as mild, or sometimes moderate, hypertension. 

In patients suspected of having a neoplasm of the adrenal medulla that is secreting excessive quantities of epinephrine or norepinephrine (a pheochromocytoma), either the catecholamines themselves (epinephrine, norepinephrine, and dopamine) or their metabolites (the metanephrines and vanillylmandelic acid, VMA) may be measured in a 24-hour urine collection, or the level of catecholamines in the blood may be measured. A patient who has consistently elevated levels in the blood or urine should be considered to have a pheochromocytoma, particularly if the patient has signs and symptoms of catecholamine excess, such as excessive sweating, palpitations, tremulousness, and hypertension. 

Metanephrine and normetanephrine are deactivated O-methyl metabolites of epinephrine and norepinephrine, produced by the action of catechol O-methyl transferase. Both metanephrine and normetanephrine are produced at low concentrations from normal metabolism of catecholamines by the sympathetic nervous system, but their concentration can be greatly elevated by catecholamine-producing tumors, such as pheochromocytomas. Pheochromocytomas are rare malignancies that often present with symptoms of catecholamine excess, most prominently h5q)ertension. When used to identify pheochromocytoma, therefore. 

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