Sodium Imbalance - Tells what it is, what parts of the body are involved, symptoms and causes of low and high sodium levels. - http://www.doctoronline.nhs.uk/masterwebsite1Asp/targetpages/specialts/gen_med/sodium_i.asp
Sodium - Merck Manual explains why this mineral is necessary, how the system regulates levels, and how the adrenal and pituitary glands effect sodium. Includes sections on hyponatremia and hypernatremia. - http://www.merck.com/mmhe/sec12/ch155/ch155k.html