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Central Diabetes Insipidus
Aka: Central Diabetes Insipidus, Central DI
- Definition
- Antidiuretic Hormone (ADH) deficiency
- Pathophysiology
- Polyuria
- Decreased ADH release
- Permanent Polyuria
- Central lesion above median eminence
- Transient Polyuria
- Central lesion below median eminence
- ADH passes via hypothalamus to portal capillaries
- Results in ADH release below the median eminence
- Etiology
- Idiopathic (30%)
- Autoimmune disease (common)
- Lymphocyte inflammation
- Pituitary stalk (thickened stalk on MRI)
- Posterior pituitary
- Anterior Pituitary deficiency
- Growth Hormone
- ACTH deficient
- Familial Diabetes Insipidus (very rare)
- Point mutation in ADH precursor gene
- Precursor accumulates
- Toxicity to ADH synthesizing cells
- Enhancement within hypothalamus on MRI
- Neurosurgery (Transsphenoidal)
- Results from Hypothalamus or Pituitary trauma
- Most common cause of polyuria post neurosurgery
- Differential Diagnosis
- Excess fluids
- Mannitol
- Corticosteroids
- Approach
- Check Urine Osmolality
- Observe response to water restriction
- Malignancy
- Examples: Lung Cancer, Leukemia, Lymphoma
- Polyuria may be presenting symptom
- Langerhans Histiocytosis (Histiocytosis X)
- Infiltrative disease
- Sarcoidosis causes similar infiltration
- Post SVT resolution
- Anorexia Nervosa
- Pregnancy exacerbates any of above forms
- Diagnosis
- Fluid Deprivation Test
- No response to water deprivation
- Response to exogenous ADH administration
- Hare-Hickey Test
- Decreased ADH to Serum Osmolality ratio
- Radiology: MRI Head
- Central DI: Diminished signal at posterior pituitary
- Management
- General Measures that potentiate ADH
- Low sodium diet
- NSAIDs
- dDAVP (Desmopressin)
- Synthetic ADH replacement hormone
- dDAVP 10 to 20 ug bid intranasally
- Chlorpropamide 125-250 mg PO qd-bid
- Antidiuretic effect - may lower Urine output by 50%
- Risk of Hypoglycemia at higher doses
- Carbamazepine 100-300 mg bid
- Enhances ADH response
- May lower urine output by 50%
- Hydrochlorothiazide with low salt intake
- Decreases polyuria
- Dose: 25 mg qd to bid