Sodium is an important mineral for the body. It carries a strongly positive charge; a charged mineral is known as an electrolyte. Sodium is found in higher concentrations inside of cells than outside of cells. Since it plays so many important roles in the body, a low sodium level can cause a number of symptoms, and can have many different causes.
Regulation and Functions of Sodium
Sodium is regulated by a number of body systems. The nervous system, including the brain and taste nerves of the tongue help regulate sodium levels by changing the appetite for salty food or thirst for water. The digestive system absorbs salt, and the kidneys regulate its secretion. Tight regulation of sodium is important because the electrolyte regulates the volume of water in the body and helps nerves, muscles and other cells conduct electrical charges.
Classification of Low Sodium
Low sodium, also known in medical terminology as hyponatremia, is classified by how much water is in the body along with the low sodium, and how long it has persisted. Hypovolemic hyponatremia means there is a low volume of water in the body along with low sodium. Euvolemic hyponatremia means there is a normal volume of water, and hypervolemic hypernatremia means there is an excess of water along with low sodium. Acute hyponatremia means the low sodium has occurred rapidly, while chronic hypernatremia means it has occurred slowly and is persisting. Therefore, acute hypovolemic hyponatremia means a low sodium level that occurred quickly and is associated with low water volume in the body.
Causes of Low Sodium
Low water volume and low sodium together, or hypovolemic hyponatremia, is caused by excessive sweating or blood loss. Euvolemic hyponatremia, normal volume of water and low sodium is caused by certain medications and long-term, ongoing diseases such as cancer. High levels of water and low levels of sodium, hypervolemic hypernatremia, is commonly caused by kidney, liver or heart disease. Hormonal changes are also a common cause.
Symptoms of Low Sodium
Mild to moderately low sodium may not cause any symptoms or signs. Acutely low sodium is more likely to cause symptoms than chronically low sodium, because the body is able to adjust to low sodium to a degree. As the sodium level lowers, a person may experience GI symptoms such as nausea and vomiting and loss of appetite. They may become fatigued, experience headaches, confusion, irritability and muscle cramps or weakness. Very low levels can induce seizures, coma or death.
References
- "Physiology"; Linda S.Costanzo; 4th Ed 2008
- "Harrison's Principles of Internal Medicine"; Anthony S Fauci, et al.; 17th Ed 2008
- "Robbins and Cotran Pathologic Basis of Disease"; Vinay Kumar, et al.; 8th Ed 2009
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