By controlling blood volume, the kidneys provide a hormonal mechanism for controlling blood pressure. The kidneys' reninangiotensinaldosterone system controls blood volume. The juxtaglomerular cells in the kidneys produce renin into the bloodstream in reaction to increased blood pressure. The kidneys assist to control blood pressure by removing waste materials and excess water from the body. Vitamin D is activated, which aids in the maintenance of strong bones. They create erythropoietin, a hormone required for red blood cell formation. The endocrine system is a collection of glands that release hormones that the body employs for a variety of purposes, including blood pressure regulation. High blood pressure can be caused by the adrenal glands producing too much aldosterone, cortisol, or chemicals related to adrenaline.