Conjugation of catecholamines, a variable to be accounted for in human hypertension

A subgroup of essential hypertensive (EH) patients with high sympathetic tone had low plasma conjugated norepinephrine (NE) and epinephrine (E), but elevated free NE and E and a hyperresponsiveness to various stimuli to the autonomic nervous system. Pheochromocytoma patients could also be divided according to conjugated NE + E levels, this time into normal and elevated conjugated groups. The latter seem to be somewhat protected by the conjugation, showing less free NE and E 'flooding' during hypertensive crises and lower VMA excretion. The degree of catecholamine conjugation can thus modify the sympathetic tone in hypertension.