CHAPTER 8 Endocrine System^345
Diabetes Insipidus
WHAT WENT WRONG?
Either a decrease in the production of an antidiuretic hormone (ADH) by the hypo-
thalamus or an increase in the production of ADH by the pituitary compromises
the ability of the kidneys to concentrate urine. This results in the excretion of large
amounts of diluted urine. The patient then drinks large amounts of fluid to replace
the increased urine output.
PROGNOSIS
Treatment will eliminate the symptoms of diabetes insipidus and the patient can
expect a normal life span.
HALLMARK SIGNS AND SYMPTOMS
- Increased urination as the kidneys fail to concentrate urine
- Increased thirst as the body attempts to replace lost fluid
INTERPRETING TEST RESULTS
- Normal blood glucose indicating that diabetes insipidus isn’t a complication
of diabetes mellitus. - Low specific gravity in urine due to increased fluid in the urine.
- Increased BUN, indicating dehydration because the concentration of solutes
to fluid is rising. - Electrolytes indicate dehydration; Na and Cl will rise as the concentration
increases. - Vasopressin challenge test. Those patients with diabetes insipidus will note
a decrease in output and thirst. - If urine output decreases and urine specific gravity increases, then the prob-
lem is with the pituitary gland and kidneys are normal. - If urine output remains unchanged and urine specific gravity remains low,
then the pituitary gland is normal and the kidneys are the problem. - Presence of a pituitary tumor or hypothalamus tumor appear on an MRI.
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