Orthostatic intolerance and postural tachycardia syndrome: new insights into pathophysiology and treatment.

Orthostatic intolerance is characterized by symptoms of light-headedness or syncope that is provoked upon standing or in an upright posture. It is most commonly caused by postural orthostatic tachycardia syndrome (POTS) or orthostatic hypotension (OH). Its pathophysiology is complex and commonly involves abnormal autonomic nervous system regulation, autoimmunity, a hyperadrenergic state, and hypovolemia. This article reviews the pathophysiology underlying orthostatic intolerance, as well as the current treatment available.