Sodium is an important mineral found in abundance outside the cell and helps regulate blood volume and pressure. Think of it as a "water magnet." For example, an increase in blood sodium concentration results in the shifting of water into the blood. Change in blood sodium can cause cells to either swell up or shrink down. Blood sodium concentration is influenced indirectly by angiotensin, anti-diuretic hormones and directly by mineralocorticoids.
Angiotensin is the active form of angiotensinogen, which is produced by the liver. The increase in angiotensin is triggered by mechanisms in the kidneys that sense a decrease in sodium. The production of angiotensin, ultimately results in the increased stimulation of the adrenal glands to release aldosterone — a secondary hormone that increases sodium the absorption in the kidneys.
Antidiuretic hormone, or ADH, is produced by the hypothalamus and released by the posterior pituitary gland as a result of either low blood volume or increased sodium concentration. When released, ADH acts in the kidneys to increase the reabsorption of water. In some people, ADH is secreted in excess, resulting in decrease blood sodium. Small cell lung cancer is a common cause of excess ADH secretion.
This class of hormones is chiefly involved in the direct regulation of sodium and potassium — contrary to ADH, which regulates sodium indirectly by increasing water reabsorption in kidney. Aldosterone is the most important mineralocorticoid in the body and is produced in the adrenal gland. Aldosterone stimulates the increase of sodium reabsorption and potassium excretion in the kidneys. In some people, Aldosterone is secreted in excess, resulting in an increase in blood sodium.
Signs and Symptoms of Abnormal Sodium
Symptoms associated with low blood sodium include nausea, confusion, headache, restlessness, drowsiness and coma. A person with high blood sodium may also experience nausea, vomiting, lack of appetite, increased thirst and weakness; and, when severe, elevated blood sodium can lead to muscles spasms, irritability, confusion, seizures and even coma.