REN and hypotensive disorder: ADH: anti-diuretic hormone (vasopressin); ANS: autonomic nervous system; BP: blood pressure; MSA: multiple system atrophy; NE: norepinephrine; PAF: pure autonomic failure; PD: Parkinson’s disease; RAAS: renin-angiotensin-aldosterone system; SBP: systolic blood pressure; OH: orthostatic hypotension