Syndrome of inappropriate antidiuretic hormone secretion (SIADH)

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What is Syndrome of inappropriate antidiuretic hormone secretion?

Syndrome of Inappropriate ADH secretion (SIADH) is the continued ADH secretion in spite of plasma hypotonicity and a normal or expanded plasma volume.

Syndrome of inappropriate antidiuretic hormone secretion; SIADH

Who gets Syndrome of inappropriate antidiuretic hormone secretion?

Hyponatraemia is relatively common. Its prevalence in hospitalized patients is approximately 2.5% and about one third of these have SIADH.

Predisposing Factors

Causes:

Cancer - Many tumours. Most common is small cell cancer of the lung.
Brain - Meningitis, cerebral abscess, head injury, tumour.
Lung - Pneumonia, tuberculosis, lung abscess.
Metabolic - Porphyria, alcohol withdrawal.
Drugs - Opiates, chlorpropramide, carbamezapine, vincristine.

Progression

In most patients the course of this syndrome follows that of the underlying disease. Sometimes, for unknown reasons, the syndrome improves even if the causative disorder deterioates or improves only slightly. This is seen particularly in strokes and other brain injuries.

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