NBME 21

nbme21/Block 4/Question#10

A 64-year-old man is evaluated for cough, dyspnea, ...

Hyponatremia

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submitted by haliburton(0),

Small cell lung cancer causes SIADH. Location + exclusionary clues.

mcl  To expand, SIADH may also result in euvolemic hyponatremia. This is because, as we know, ADH increases absorption of water and therefore initially results in an increased circulating volume. However, this results in increased stretch of the atria and subsequent secretion of ANP. ANP (atrial natriuretic peptide) then results in loss of sodium and water.