Hyponatremia occurs as a result of certain diseases of the heart, kidney and liver, excessive water intake, hormonal changes, and certain medications, notes Mayo Clinic. Dehydration, chronic diarrhea and vomiting may also cause hyponatremia. These conditions cause the level of sodium in the body to reduce to below normal.
Hyponatremia results from an abnormally low level of sodium in the body, usually below 135 milliequivalents per liter, according to Mayo Clinic. Heart diseases such as congestive heart failure cause accumulation of fluids in the body, which in turn cause dilution of the sodium in the body. The dilution reduces the quantity of sodium in the body, leading to hyponatremia. Specific kidney and liver diseases also lower the level of sodium in a similar way.
Hormonal changes may deprive the body of the ability to maintain proper sodium level, explains Mayo Clinic. For instance, the adrenal gland, which produces hormones that regulate the level of sodium in the body, may fail to produce enough hormones as a result of conditions such as Addison's disease, leading to hyponatremia. Insufficient production of thyroid hormone also leads to low sodium level.
Medications that cause hyponatremia include specific diuretics, pain killers and antidepressants, says Mayo Clinic. These medications result in excessive sweating and urination, hence lowering the blood sodium level.