They are part of the endocrine system, a group of glands that produce and secrete hormones that act on and regulate many systems throughout the body. Aldosterone is produced by the outer layer of the adrenal glands, the cortex. It is a hormone that plays an important role in maintaining blood volume, pressure, and electrolyte balance. Its production is normally regulated by renin, an enzyme produced in the kidneys. Aldosterone increases when renin increases due to low blood pressure, decreased blood flow to the kidneys, or a sodium deficiency. When renin decreases, aldosterone also decreases.