- M Myeloma 
 - circulating volume decreases (ADH stiumulated), total volume increases
 - CHF, Cirrhosis, Renal Failure
 - SIADH  (ADH stimulated)
 - Adrenal failure, Beer potomania, Hypothyroidism, Nausea, Pain, PNA
 - Volume depletion (ADH stimulated)
To distinguish the Hypotonic Hypervolemic entities just remember this:
Normal UNa = 25 mEq/L - 50 mEq/L
Normal Uosm = 40 - 1400 mOSM/kg H20
Renal Failure will p/w high UNa and dilute urine.
Cirrhosis will p/w low UNa and concentrated urine.
CHF will p/w low UNa and conentrated urine.

What's the diff for hyponatremia ? REF

HCTZ causes hyponatremia and hypokalemia along with the hyerGLUCS. 

What is Conivaptan (Vaprisol) ? REF