Sodium metabolism

Hypernatremia

Hyponatremia

WikEM overview on hyponatremia: https://www.wikem.org/wiki/Hyponatremia

Quick hits on hyponatremia: http://lifeinthefastlane.com/ccc/hyponatraemia/

Another good hyponatremia overview (with some links to cases): http://lifeinthefastlane.com/investigations/hyponatraemia/