Hypovolemic hyponatremia?,”Hypovolemic hyponatremia can be due to acute blood loss, renal (eg, diuretics) or GI (eg, diarrhea, vomiting) volume loss, or primary adrenal insufficiency. Volume depletion from these conditions results in loss of both sodium and water. Hypovolemia decreases effective arterial volume to the kidney, which activates the renin-angiotensin-aldosterone system. This leads to increased renin, angiotensin
and aldosterone levels. Increased sodium and osmolar levels in the blood stimulates ADH release from the pituitary. The elevated ADH increases renal water reabsorption to cause hyponatremia until correction of the hypovolemia.”