1. (Vasopressin) aka: Antidiuretic Hormone aka: Arginine Vasopressin

2. Vasopressin
Amino acid sequence for Vasopressin is Cys-Tyr-Phe-Gln-Asn-Cys-Pro-Arg-Gly
The single most important effect of Vasopressin is to conserve body water by reducing the loss of water in urine.
Since it is a anitdiuretic it counter acts diuretics (responsible for water loss in the human system)

3. Vasopressin and kidneys
Vasopressin stimulates water reabsorbtion by stimulating "water channels" (aquaporins) into the membranes of kidney tubules.
Aquaporins have many different functions but are in parts of the body to regulate fluid

4. Diabetes
The most common disease due to a lack of vasopressin is diabetes insipidus
Without vasopressin the amount of urinations made daily increases to such amounts as 4.2 gallons of urine a day.
The increase of urination is due to the decrease of the amount of water that can be held in the kidneys.

5. sources
 website contains 3D vasopressin model