Sympathetic Activity and Cardiometabolic Complications

Catecholamines (noradrenaline, adrenaline and dopamine) are adaptive and maladaptive stress hormones. In the classic "fight or flight" mechanism, they activate behavioral and physiological processes that facilitate the overcoming of stress; for instance, challenged by a physical stressor, an organism responds to the threat either fighting and prevailing or accepting defeat and fleeing in avoidance. In the pathological context, an excessive catecholamine secretion is typical of the chromaffin tissue tumors, determining a clinical picture characterized by blood pressure elevation, tachycardia, anxiety, pallor, sweating and headache. COMT enzyme catalyzes the O-methylation of the 3-hydroxyl group of catecholamines. The O-methylated derivatives of noradrenaline, adrenaline and dopamine are normetanephrine, metanephrine and 3-methoxytyramine, respectively. The term "metanephrines" is generally used to collectively refer to the first two compounds. Compared to catecholamines, metanephrines are characterized by longer half-life and more stable levels over time. Their superior accuracy for the diagnosis and follow-up of pheochromocytoma and paraganglioma (PPGL) has been widely proved. Excluding patients with PPGL, however, metanephrines can be more broadly considered as reliable markers of the whole sympathetic system activity; therefore, their levels may be hypothesized to be associated to a higher rate of concurrent cardiometabolic complications and, if so, could be useful for the stratification of cardiovascular risk.