While a few studies in our review did evaluate changes in renin-angiotensin system and arterial baroreflex pathways, other mechanisms are known to be altered in POTS that could be influenced by exercise including changes in neuroendocrine, metabolic, hormonal and immune pathways, each meriting additional investigation as to potential POTS-specific mechanisms of exercise benefit. The gene discussed is REN; the disease is postural orthostatic tachycardia syndrome.