All of the following are impoant causes of hyponatremia, EXCEPT:
Excess sweating is associated with the development of hypernatremia. Hypernatremia is defined as a sodium concentration > 145 mEq/L. All patients with hypernatremia have hyperosmolality. The hypernatremic patient is typically hypovolemic due to free water losses. Hyponatremia is defined as serum sodium concentration < 135 mEq/L. Cause of hyponatremia depends on patient's volume status and serum osmolality. It is classified into hypervolumeic, euvolemic and hypovolemic hyponatremia. Hyponatremia reflects excess water retention relative to sodium rather than sodium deficiency. Causes of hyponatremia are indicated in the table given below. Ref: Current Medical Diagnosis and Treatment, 2012, Chapter 21
Gastric fistula
Excessive vomiting
Excessive sweating
Hypothyroidism