Dipsogenic DI occurs when vasopressin is suppressed by excessive intake of fluids.  The latter is usually referred to as primary polydipsia and is most often caused by an abnormality in the part of the brain that regulates thirst.   This subtype is called dipsogenic DI and is difficult to differentiate from pituitary DI particularly since the two disorders can result from many of the same brain diseases.  The only sure way to tell them apart is to measure vasopressin during a stimulus such as fluid deprivation or to observe the effects of DDAVP treatment.  In dipsogenic DI, DDAVP also eliminates the excessive urination but, unlike pituitary DI, it does not completely eliminate the increased thirst and fluid intake.  Thus, it also results in water intoxication, a condition associated with symptoms such as headache, loss of appetite, lethargy and nausea and signs such as an abnormally large decrease in the plasma sodium concentration (hyponatremia).   Because of this and the current lack of a way to correct the underlying abnormality in thirst, dipsogenic DI cannot be treated at present, although the most troubling symptoms, nocturia, can be safely relieved by taking small doses of DDAVP at bedtime.   The other subtype of primary polydipsia is due not to abnormal thirst but to psychosomatic causes and is often referred to as pyschogenic polydipsia.   It cannot be treated at present.

Return to 4 Types of DI to read personal stories and articles about DI. Some of the information is common to all 4 types of DI, others are particular to a specific type of DI.