Besides cardiovascular autonomic dysfunction, several potential mechanisms are involved in the development of PPH: Increased splanchnic blood pooling, age or HT-related decreased baroreflex function, inadequate sympathetic nerve firing or vascular responsiveness to norepinephrine, upregulation of vasoactive intestinal peptides, and insulin-mediated vasodilation [27]. This evidence concerns the gene INS and Abnormal autonomic nervous system physiology.