What is the action of the vasopressin hormone released from the client's posterior pituitary gland?

Vasopressin, or the other name Anti Diuretic Hormone (ADH), has the action of causing the opposite (anti) of a diuretic. I.e., it causes the body to retain sodium, thus retaining water. This has many physiological effects, the majority of which focus around enabling the body to maintain homeostasis when water intake or hydration levels drop.