ABSTRACT
The physiological regulation of blood pressure (BP) is a very complex interplay between cardiac, vascular, renal, neural, and endocrine factors modulated by genetic and environmental factors. Thus, hypertension which, is a disorder characterized by a sustained increase in BP above a predefined normal range of values, can result from any imbalance between these regulatory mechanisms. Numerous humoral and endocrine factors have an impact on BP and, hence, have been considered as potential pathophysiological causes of hypertension. Among them, the sympathetic nervous system and the renin-angiotensin-aldosterone system (RAAS), which are discussed in the two preceding chapters, play a pivotal role in the regulation of vascular tone, and an inappropriate activity of these systems definitively contributes to the development and maintenance of secondary forms of hypertension, such as renovascular hypertension, primary hyperaldosteronism, or hypertension secondary to a pheochromocytoma. However, besides these two major systems, several other hormones and vasoactive substances affect BP control and may lead to hypertension either through a direct effect on the vasculature or by interfering with the renal handling of sodium. In many cases, these hormones also interact with the RAAS and the sympathetic nervous systems. As an increase in BP can result from an increased activity of vasoconstrictor systems, as well as from a decreased activity of vasodilating factors, this chapter discusses the humoral and endocrine factors, which promote or prevent sustained increases in BP, and thereby may contribute to the etiology of hypertension.
