Huh? Yeah, that's what I said to myself initially too but there's a case presentation of a pheo presenting with orthostatic hypotention in
this week's New England Journal of Medicine. This supposedly occurs because the pheo causes down-regulation of the receptors in the sympathoadrenal system which is responsible for maintaining cerebral perfusion in the upright posture. Makes sense I suppose.
Causes of orthostatic hypotention:
- volume depletion
- autonomic neuropathy (parkinsonism, diabetic neuropathy)
- pharmacologic blockade of receptors used by the sympathoadrenal system
- down-regulation of these same receptors because of chronic exposure (pheochromocytoma)
Source
Samuels, M. et al. "Case 14-2010: A 54-Year-Old Woman with Dizziness and Falls" N Engl J Med 2010.