Diabetes Insipidus
Diabetes insipidus is excessive urination and thirst from a problem with vasopressin (the hormone that helps the kidneys conserve water) -- central (the brain doesn't make enough) or nephrogenic (the kidneys don't respond to it), per current disease primers.
Symptoms
Excessive urination (more than 3 liters a day) and excessive thirst, often disrupting sleep with frequent nighttime urination.
Causes and risk
Central DI follows pituitary surgery, head trauma, or tumors; nephrogenic DI can be genetic or caused by certain medications (lithium especially) or kidney disease.
How it is evaluated
A water deprivation test is the traditional approach (roughly 70% accurate); stimulated copeptin testing, a newer method, is over 90% accurate and increasingly preferred where available, per recent NEJM data.
Treatment
Desmopressin treats central DI effectively; nephrogenic DI, since it doesn't respond to vasopressin, is managed differently (thiazide diuretics, low-salt diet). Post-surgical central DI is often transient and may resolve without lifelong treatment.
When to seek care
Severe dehydration or a rapidly rising sodium level, especially if fluid intake can't keep pace with urination, needs urgent evaluation -- sodium correction that happens too fast or too slow both carry real risks, so this isn't something to manage without guidance.