Dipsogen

A dipsogen is an agent that causes thirst. (From Greek dypsa, "thirst" and the suffix -gen, "to create".)

Physiology
Angiotensin II is thought to be a powerful dipsogen, and is one of the products of the renin-angiotensin pathway, a biological homeostatic mechanism for the regulation of electrolytes and water.

External references
'Fluid Physiology' by Kerry Brandis -from http://www.anaesthesiamcq.com