A hormone produced by the adrenal glands (see corticosteroid); it controls excretion of sodium by the kidneys and forms part of the renin–angiotensin–aldosterone system, which regulates blood volume and blood pressure (see renin). Aldosterone promotes the reabsorption of sodium ions from the collecting ducts and distal tubules of nephrons in the kidneys, thereby causing enhanced reabsorption of water. See also angiotensin.