Sodium is an abundant mineral in the diet, derived mainly from consumption of salt. Within the body, sodium takes on a positive electrical charge becoming an electrolyte--a chemical capable of transmitting electrical messages. Sodium is the most abundant, positively charged electrolyte in the circulation. Low sodium levels, or hyponatremia, can cause widespread chemical abnormalities throughout the body. Causes of low sodium most commonly involve either abnormal losses of sodium, or total body water overload.
Syndrome of Inappropriate Antidiuretic Hormone Secretion
The pituitary gland normally produces and secretes antidiuretic hormone, which acts on the kidneys, causing increased water retention. The syndrome of inappropriate antidiuretic hormone secretion, or SIADH, occurs when there is excessive antidiuretic hormone in the circulation, causing inordinate water retention. The increased water dilutes the concentration of sodium in the circulation causing hyponatremia. The University of Virginia Health System explains a variety of conditions can cause SIADH, including head trauma, brain infection, meningitis, multiple sclerosis, Guillain-Barré syndrome and pituitary tumors.
Adrenal Insufficiency
The adrenal glands secrete the hormone aldosterone, which acts on the kidneys, causing retention of sodium. The National Institute of Diabetes and Digestive and Kidney Diseases explains that with adrenal insufficiency, also known as Addison's disease, the adrenals cannot produce adequate amounts of aldosterone. Excessive sodium is lost in the urine, leading to hyponatremia.
Kidney Disease
The Merck Manual for Healthcare Professionals points out that a variety of kidney disorders can upset the balance of sodium and water in the body, leading to hyponatremia. Examples include nephrotic syndrome, medullary cystic disease, polycystic kidney disease, interstitial nephritis and chronic kidney failure.
Heart and Liver Failure
In an article on the management of hyponatremia published in "American Family Physician," Dr. K. P. Goh notes that congestive heart failure and liver failure can cause increased total body water, which dilutes the circulating level of sodium. Correcting the total body water overload leads to normalization of the sodium level.
Severe Vomiting or Diarrhea
Severe and persistent vomiting or diarrhea may cause a low sodium level, advises Penn State College of Medicine's Hershey Medical Center. With these conditions, both sodium and body water are lost in large quantities, but with proportionally more sodium than water.
Drugs
Drugs can disturb sodium and water balance in the body. The Mayo Clinic points out that diuretics, which are commonly used to treat high blood pressure, cause salt wasting by the kidneys. Overuse of diuretics or inadequate dietary intake to replace urinary losses may result in hyponatremia. The recreational drug methylenedioxymethamphetamine, better known as MDMA or Ecstasy, can cause significant hyponatremia, especially when the drug is taken with alcohol. Hyponatremia-related fatalities associated with the use of MDMA have occurred.
References
- Mayo Clinic: Hyponatremia, Causes
- American Family Physician: Management of Hyponatremia
- Merck Manual for Healthcare Professionals: Hyponatremia
- Penn State College of Medicine, Hershey Medical Center: Hyponatremia
- National Institute of Diabetes and Digestive and Kidney Diseases: Adrenal Insufficiency and Addison's Disease
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