Hyponatremia

If serum Osm > 290
- Hyperglycemia
- Advanced renal failure
If serum Osm < 290
- If urine Osm < 100
  - Polydispia
  - Beer potomania
- If urine Osm > 100
  - Urine Na > 25
    - SIADH
    - Adrenal insufficiency
    - Hypothyroidism
  - Urine Na < 25
    - Volume depletion
    - CHF
    - Cirrhosis