MEDizzy - A 10-yr-old boy receiving vincristine for treatment of a

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Endocrine

A 10-yr-old boy receiving vincristine for treatment of a malignancy has developed the syndrome of inappropriate antidiuretic hormone secretion (SIADH), a known complication of this therapy. All of the following parameters would be decreased in this patient except:

ExplanationThe pathophysiologic mechanism is excessive free water retention and dilutional hyponatremia. Other causes of dilutional hyponatremia such as heart failure or cirrhosis are characterized by a reduction in effective renal blood flow. This is not a problem in SIADH.