Internal Medicine

P1: RLJ/OZN P2: KUF

0521779407-D-01 CUNY1086/Karliner 0 521 77940 7 June 13, 2007 7:41

Diabetes Insipidus 471

Imaging

■MRI of the pituitary and brain: normal posterior pituitary bright spot

on T1 imaging absent in DI

differential diagnosis

■Idiopathic DI

■Primary polydipsia (psychogenic water drinking)

■Nephrogenic diabetes insipidus: congenital, hypercalcemia, lithium

use, hypokalemia

■Diabetes mellitus

■In pregnancy, excess vasopressinase from placenta

■Pituitary tumor

■Hypothalamic mass: craniopharyngioma, dysgerminoma, metas-

tases

■Granulomatous disease and histiocytosis

■Pituitary apoplexy

management

What to Do First

■Treat with DDAVP (parenteral, nasal spray, or tablet)

■Volume and free water replacement

■Rule out nephrogenic DI, hypercalcemia, and diabetes mellitus

■Evaluate pituitary and hypothalamus by MRI

General Measures

■Normalize serum sodium

■Treat hormone deficiencies and excesses

■Normalize serum calcium, glucose

specific therapy

■Hormone replacement therapy with DDAVP, which has only ADH

activity, not pressor (AVP) or oxytocin-like activity

■Replace other hormones as needed: cortisol, thyroid hormone,

testosterone, estrogen/progestin, GH

■Surgery for craniopharyngioma

■Radiation therapy for dysgerminoma

Side Effects & Contraindications

■Surgery and radiation side effects: panhypopituitarism, CNS injury

follow-up

■Measurements of serum sodium

■Repeat pituitary MRI after 3–6 mo to assess tumor growth