Aldosterone is a steroid hormone (mineralocorticoid family) produced by the outer-section (zona glomerulosa) of the adrenal cortex in the adrenal gland to regulate the bodies electrolyte and water balance. It is synthesized from cholesterol by aldosterone synthase, which is absent in other sections of the adrenal gland. It acts directly on the kidney to decrease the rate of sodium-ion excretion (with accompanying retention of water), and to increase the rate of potassium-ion excretion.